Alright, thanks folks for joining in. Tom, this conference, you know, I happened to start this back in 2004. We've been running this. And so over the years, you would see that, you know, there are quite a few people that have been part of this community helped us build this. And, you know, that's where you see a lot of these familiar names folks who kind of come back. And I'm sure everyone has been waiting for this opportunity to meet you, unfortunately, not in person but, you know, virtually at least. It's such an honor and it's such a privilege Tom to finally have you, you know, talk to talk to the agile India community. Tom is someone that again, most of us have been deeply influenced by Tom's work. I remember, you know, back in like many years ago someone gave me your software metrics book because that was one of the area that I was pretty keen on in terms of measuring, you know, what we are doing and when we're trying to go there we go. Absolutely. And this has been such a such an instrumental book, Tom, in a lot of work that we do in fact, even just a few months ago there's a bit of an open source project that I built where we try and, you know, measure some of these metrics in there from the book as well. And I was referring to like this, this work is, is before I was born, this work was that before I was born, which is pretty cool right so. And I think you can also talk about some of your work with with the Indian government and data and your role you played in CMM for. So, you know, again, I think it's just a great honor to have you Tom and looking forward to to your talk. And without much delay I'm going to hand it over to Tom. Right. So here is our title agile engineering. So I'm going to try to put the engineering in agile, because it's not there yet. And we don't need engineering for very simple small projects, but we need engineering for the large complex ones that are facing almost everybody. I have about 37 slides. I'm going to go as obviously a pace of about one slide a minute. And many of my slides have a lot of detail in them. And you will not have time and I will not have time to go through the slides in detail. So I will present a highlight and if it interests you, you can go back and get a copy of the slides and study them later and you will find very many free books and papers to allow you to go into more depth in the projects that interest you. I have a photo of me with the early books from 76 and 88. And they both contain considerable agile information. I'll give you a sample in a moment. But the, we didn't call it agile for many quarter of a century we called it evolutionary delivery, even the US Department of Defense called it that it had special standards for it. So but agile is the popular term that my friends agreed on. If you want a copy of the slides you'll find them at the conference site you'll also find them here.  This is a collection of very many things I've written papers and talks mostly, but videos on agile, you can use this qr to get a hold of it. So, I couldn't resist putting this picture in. Sorry, one picture too many. I think. Okay. Well, there's a picture of me at my son Kai, who lectured at agile India recently, his wedding at Shri Shri Ravish tankars ashram in Bangalore, and my wife and I, and my older son are also in the Indian costume. Shortly after the wedding I went to an IT conference in Bangalore, and everybody had to have a picture with me because I saw tall.  So I consider myself an amateur Indian Prince. Here's the agenda about 16 subjects, about 45 minutes. And we, and then there's also the link to the agile library there. Okay, so I would like to quote to you from the book where metrics book the US edition came out in 77. And from page 214, and I'm quite proud of what was there, because I think it not only defines agile, but it defines agile as it should be, and is not. That is, there is some engineering here, a complex system, which is what we're interested in for engineering will be most successful if it is implemented in small steps. No surprise. That's the basic idea that everybody agrees to with agile small steps. And if each step has a clear measure. Metrics measurement software metrics book engineering, a clear measure of successful achievement. For example, if we're trying our project is trying to enhance the security of the system, we should be measuring security increases at every sprint. Got it. Do you do things like that. As well as a retreat possibility to a previous successful step upon failure. So a step can fail, but we need to be able to retreat and go back. So, this is also my recipe for always being successful and never failing on a large scale. So, yeah, so my first point is there is far too much emphasis on coding and being a coder and writing code as the environment for agile. And I think there are a lot of other things we have to worry about. We have to worry about the data and the databases. We have to worry about the people using the system customers of the system and the other stakeholders. We have to worry about the hardware. We have to worry about I have a special name for programmers soft crafters, not software engineers. They're not engineers. They are craftspeople. I hope they are very good craftspeople, but they are soft crafters and plumbers and electricians do not make a skyscraper of 100 stories engineers and architects do. Okay. And there is even legal things laws we have to respect. And cultures we have to respect. So, there's just a whole lot of things more than the logic where more than the code and we and what I see is everybody is thinking about the code and writing the code and things like that. They're thinking like soft crafters programmers, but they're not thinking about the systems. Okay. So we need systems level thinking, even if our main job is programming and our main interest is the code somebody. Let's call them the systems engineer, the project manager. There, there is no word for this at all in things like scrub product owner really is nowhere near this case you wonder take a look at the description. We need somebody to manage the system. Let's call them a product owner and to architect the system. Let's call them the systems architect. And in fact, we need to do what is called systems engineering. Point number three of 15 stakeholders and I'll get back to this later. But let me give you a little first definition stakeholders are anybody or anything, which has a requirement for your system. Okay, so a law which says you must protect privacy is a stakeholder. It's not a person, but it has a requirement for you. So here is a long list of stakeholders. Every medium and large scale project has at least this many critical stakeholders critical means, if you don't make them happy, they can kill your entire system. They can make it illegal. They can make it so nobody can buy it or use it. Okay, so I believe we need to move away from users and customers and user stories as too little. We need to move over to stakeholder experience, not user experience stakeholder stories, not user stories. We need to. This is part of being systems engineer. We need to take into consideration all those factors, which determine whether we succeed, or fail. If we only look at the code, we fail. Look at the fader rates Google agile fader rates standish group for example, and you find horrendously high fader rates, due to, in my opinion, not using these engineering methods and being too much of a programmer and too little of an engineer. There's something else here. Many stakeholders, many qualities or values I call them these are stakeholder values these are the top 10 critical ones they're all quantified in my world. These are the costs, for example, future maintenance costs not just capital costs. And these are the top level architecture or strategies, and each one of these is related to one or more qualities is related to one or more costs is really and the qualities is what we're delivering back to the stakeholders. Okay, the qualities are the values that the stakeholders have. So it's a pretty complex picture, and we're using an app or a tool to keep track of it here called val plan. Point number four. If we have to think in terms of the cost effectiveness of our systems. Now, effectiveness. That's for me multiple values the security the privacy the performance the usability multiple values at the same time. And then there are multiple costs money now money later time and effort now and later. Okay, and in a way there's a little equation here, we can call efficiency. And it is the sum of all of these values, what we're giving to our stakeholders over the sum of all the costs types, all the resources. And we, in particular, our architects need to be looking at the value to cost ratio, the architecture. There's a chapter in in a book I've written I'll give you a copy of that free but there's a video going into this point more deeply. Now, this slide. Do you have an agile method that can handle 10 top objectives, quantified and five costs at the same time. Although I don't think you do. Here is a tool called an impact estimation table. It's in my books. It's in. You can. If you're interested you can read about it, but it's a tool is basically a spreadsheet. But on this axis we have any number of critical values or qualities, which are quantified. Here is how bad we are this number. Here's how good we want to be in the future. Here is a set of architecture strategies solutions designs, call them what you want. But they're the things we're going to do in our system and build or acquire in our system, which, if we do will give us some more of this value and more of this value and more of this value and more of this value and it will consume some of this cost and some of this cost. Okay, so here is actually a numeric way of looking at the multiple values of any design or architecture towards any set of quantified critical values or probabilities with respect to any set of long term short term cost people time money and using these numbers, we can actually compute the values to cost ratio, and we can point out the number here is the highest value to cost ratio. The highest value to cost ratio is a good way of prioritizing and saying, we will do this strategy first in the first prince, because it will give us the most values for the least costs. Here's a way of simplifying this table and simply bar chart. There's the sum of the values and there's the sum of the costs and these are different for different architectures being compared. I hope some of you if you get nothing you get this idea of the impact estimation table as the way of modeling complex systems and a way of engineering them. Point number six, do you have an enterprise architect. Some of you do. Many of you don't. It's not really a part of agile is it it's part of large scale systems development. Okay. Now, in this case I'm pointing to a case study from IBM systems journal from IBM federal systems division. And they had a problem. And some of you have the same problem that they had a fixed price contract with NASA or US Department of Defense for some software for maybe a ship or a rocket ship. And they had a fixed deadline for delivering it, and they had very high qualities for defense and space, the highest that were attainable. And every time they took such a contract, they lost money, they delivered light, and they had problems with the quality. So IBM went to the smartest guy in the room one hard and mills I call him the Leonardo da Vinci, a software engineering and said, Harlan, can you solve this problem. Can you always deliver on time under budget so we make money, the highest quality is for the largest most complex software systems and Harlan said, I'll try and he he spent years doing what is called the clean room method, you can look it up you can get books on it, etc. And now the one point I'm going to and they achieved that they achieved years on end, always on time. Imagine that always under the fixed price budget so they made money. Imagine that always delivering the highest qualities. Imagine that most people don't know how to do that. But this was decades ago, and reported in the IBM systems journal here is a link to the detail down here. Now, I'm going to make a very simple point here. The way they did it was none of the ways that are being taught in agile today at all. What they did, but this is agile. The their loop to deliver a navy system was 45 increments. In other words, 2% increments. Okay. Now, after every increment. They asked, are we is the quality that we want like availability of the system. Is that going up twice 99.98% that we are supposed to deliver. Yes, or no, if no, and we expected it to go up. Bob Quinn and the architect and say, Bob, you have to fix your architecture. Right now, before we do the next sprint, and you have to make it more effective so that we can can reach our architecture quality levels on on time. Or if, for example, if the one month sprint took two months, then they brought in Quinn and said, redesign the architecture. So it only takes one month. Okay. In other words, they made up to 45 adjustments in between sprints based on numeric feedback in relation to their numeric goals. And these adjustments allowed them finally to be on time under budget. Every time with the highest quality space and military systems. This should be taught in all universities for all large projects and certainly for software, but it is not the professors don't teach it. They were never taught it. They don't know about it. And this is the best agile method in the world, except Mr Musk, as I will talk to at the end, has also taken into use basically the same methods for space X and Tesla. Here's just another one. This is that they use the same iterative process to build the initial architecture as a series of steps until they think they have a good starting architecture before they do their sprints point number seven. And one of the largest adopters of my methods my planning language or plain which which quantifies the qualities and has the impact estimation table is Intel. They have been doing my methods corporate wide with over 20,000 engineers for 20 years successfully. But one man there Mr Terzakis likes to do research on my methods as they're used in practice at Intel so here's a research paper you can all have. And I give you just this one idea. So, first they, they know that a primary source of problems is badly written requirements, which then get to the architect which then does the wrong architecture. And so, basically, they do my quality control methods specification quality control. Okay, which is a simplified form of the inspection method. And they apply it to my planning language specifications which they teach everybody on a two day course. So a group comes with a 31 page requirement document, and they find 312 defects these are violations of the rules of the standards. In simple terms those standards say the requirements must be crystal clear numeric. No fluffiness. Okay. And this means that our 10 major defects per page page is 600 words, not bad actually quite good, because language forces you to have a good level to start with, but it turns out that Intel has calculated that they need to have a level of 2 per 600 words maximum. Otherwise, it doesn't pay off to go into architecture and design chips. So what they do is they say no exit your, your requirements aren't good enough, and the team tries again and again and again and again. This could be some weeks later, a 45 page requirements with only 10 defects, in other words, 0.22 gets exit, meaning it can be used for other purposes to can go to the architect. By the way, they have now reduced 98% of the incoming defects that were here in the first one. Okay, so this is a practical example of using my engineering methods in a very good engineering corporation, Intel, and there are more other corporations like Boeing and Judith Packard I could name right away. You will find case studies of my clients succeeding with the methods in the books. I'm giving you for free. Point number eight. In the way I already went through this, but maybe an enlarged version. So here we have the impact estimation table. Here we have different architectures. But in this case, we're going to consider the architectures to be possible sprint deliveries possible increments. Okay. And what we're trying to do is estimate how good is this architecture for this particular goal. And the answer is it gets us 50% of the way towards the goal. In other words, halfway between 50 and 90% of the numeric goal. And the same architecture has a beautiful side effect. It gets us 57% of the way towards this goal. And it gets us 53% of the way towards this goal. And it gets, et cetera, you see it. So wow, that's a really good design or architecture. Have you ever thought how to really evaluate a design. This is how you have to numerically say how good it will be and later measure how good it is in relation to your critical quantified objectives. As you know, the agile we know today doesn't try to do this at all. It is not engineering, and it does fail too often. And we've got to stop this failure by becoming agile engineers. You've got some great engineering universities in India. Maybe they should start teaching agile engineering. And I hope I'm talking to some of the professors right now. And I will help you with written materials and slides and any way you like to make the transition to teaching these ideas in India, if you just ask. So, yeah. And then here we have the rating of the costs. And here we have the computation and green means this has the best values for money. Therefore, we should, if we're smart, we should do this first, we should do this early. And even if it's a little bit disappointing, maybe it won't be so bad. If you take a disappointing one, and it's disappointing, maybe it's terrible. Point number nine, in simple terms, it's time we stop doing kids stuff with yellow sticky culture. It's time we digitized our thinking, as I've just shown you examples of digitized our planning for our agile systems and our management of the projects. And I'm, I am working with investing in and my methods are being used in next generation artificial intelligence, using ontology semantic triples the solid standard from Tim Berners-Lee Web 3.0. And I hope we can say bye bye yellow stickies. Those are for kids in their sandbox for small projects, no problem, but the large projects, not good enough go to graph metrics.com and take a look at that. Number 10, meet my friend Eric Simmons. He's the man who spread my methods for 20 years at Intel. He personally developed the courses taught the people coach them and also just made sure it worked in practice. He also wrote the forward to the competitive engineering book.  And I said, I don't like safe. I think safe is terrible. Badly thought out chaotic method. And I think my methods already scale up better. And he replied to me in writing. Here it is. He said, Tom, your methods don't need to scale up because they are scale free. They all and we have proven this on small and large projects at Intel in practice for 20 years. Okay. Wow. I didn't think about it that way. Now I'm writing a new book. Here's the link to I'm in the middle of writing it. It's called simple. Okay. And we have a special chapter there on scaling where I've tried to work out the theory of why are some methods scale free. They work at any scale. And why are some methods not and the simple answer is what I call black box theory methods that look outside the black box, no matter how big and complex the inside of the black box are will work at any scale. I wonder if some of you picked up the idea. Anyway, read of the black box theory of scaling of methods in my new simple book and you can follow the writing of that book. In the next few weeks, I hope to finish it. Here's just a practical example. This is the same impact estimation table in use at a very small company of total 67 people but operating on the international market with media software and development staff is 13 programmers and three testers and they've divided their people about 16 people into four four person teams. Each team takes a quantified set in this case very many usability things but here's some testability and backwards compatibility. They take some quantified goals here's the quantification, and they work on them for a quarter of a year in weekly increments, and they measure cumulatively how far they have gotten this is actually week nine of 12. So they bought 67% of this 100% of this 107% of this one, and then based on this feedback, they decide which goal they're going to work on usually the weakest ones like here's a zero. So we need to work on this is dynamic prioritization, and they achieve by the end of their deadline which is the quarterly release of the software to the world, they achieve extremely high qualities on in about 20 areas. In the first year of the use of this method, they blew away all their international competition, they wiped them out and bought them up and succeeded on the market and they directly credited on their website in public our Evo method. This is just simple proof that even on small scale agile engineering also works, you can read the detailed case study there. So, 12 principles of agile engineering. Now, let's see. How are we doing on time. We've got to be. Let's see. And I'm going to look at my watch. Yeah, okay. So we're pretty good on time. I have an alarm going in about 10 minutes end of the 45 minutes and then we have a little bit of leeway here but okay. So this is from a book called value agile and here is your free copy. Here are some slides on it and here is even a video of me explaining value agile or agile as it should be. Okay, and here are the basic principles. Now, actually I've been through these principles in my earlier part of the talk so I can save time, but I have condensed the basic idea into these 10 basic ideas, and these are the basic ideas then of agile engineering. I've been engaged with a group called Essence with Eva Jockerson who invented URL and other things.  Okay, and me too. I'm 81 years old.  And even got a great idea. He said, let's stop the agile wars of my method is best get certified in my method pay me. He said this is silly. Let's have a library called Essence, and let all those who will donate their methods, give their methods for free to everybody in India and everybody everywhere else. So for example, Scrum has done this. Okay, Jeff Sutherland. He's on board there. I have done this. And so I've taken all my methods and I wrote a special booklet you can have a copy of it, called Simplan. And actually, I'm having a meeting later this evening with the people who are moving my ideas which are organized in this book over to Essence in progress now. But if you like this book is a way of pick and choose any of the 100 micro acts, and you can bring it into your method without changing your method. Okay, one idea at a time, if it works for you, it's good, and it's free.  Okay. Now point 14 out of 15. Not too bad. Stakeholder again. So I have a, I finally did what I've been promising myself to do for years. Last year, I wrote the stakeholder engineering book, which is how many pages is it's a lot 170 pages or something like that. Here is are the principles of stakeholder engineering. Okay, one of them is the stakeholders are so many and so complex that you really need digital tools, not yellow stickies to keep track of them. And you need a very clear definition of who that stakeholder is and what values they hold, and you need numeric information, how much security do they want, and when do they want it. That's numeric information about the stakeholder values, etc. Again, if you want my one page summary about stakeholders. Here it is. Nice little diagram where I analyze stakeholders in relation to threats and security. No more time for that. And so we have must methods. Now, about a year ago, must did a star based tour. And during that tour, he said, this is my I have five principles. Here's my number one, two, three, four, five principles and I thought, wow, must hasn't yet written his methods book, but I could. This was then written down. I made my own notes but the guy with the video made his notes, and we finally wrote down must five principles. Okay, and here they are. And I like must principles because, well, because they're the same as my principles, right? But he has some fun principles, for example, requirements are wrong. It doesn't matter who gave them to you, like your customer in Europe or something like that. He says it's particularly dangerous. Even if an intelligent person like Elon Musk gave you the requirements is you might not question them and say maybe they could be improved. Everyone's wrong. Even Elon Musk. All designs are wrong. Even Elon Musk's. It's just a matter of how wrong. Wow, wow, wow. And there's more here. By the way, he ends up with everyone should be a chief engineer. What does he mean, he means the same as I started this talk with everyone should understand the larger system and how it all hangs together like Musk does when he works in detail. Okay, so he here is just a reminder that the principles of Musk are as far as I can see the same as I'm trying to encourage you my my language ideas. And I think Musk is the greatest agile practitioner of all. I think, forget me, forget my ideas. Don't read my book, read Musk's methods book, which I give you for free. I rewrote his because he was just spouting off orally while walking around his his spaceships, but I rewrote to make it clearer what I think Musk means. And I detailed here's the detail on the requirements. Here's a a language requirement in detail quantified. Okay. I rewrote the design. I rewrote the dynamic optimization. I rewrote accelerate. Here's a fun picture. Here's the chairman of Volkswagen being jealous that Musk in his German factory will go three times faster pushing the cars out. And they even dream about Volkswagen. Not bad for a beginner because I believe Volkswagen's been at it since the eye before I was born. He's pretty good. These principles work. Okay. Automate, but as some of you know, in the for the Tesla Model three must automated too much too fast and he had to go back and systematically work his way up to automation or not automate very interesting study I drive the Tesla Model three for one year now. It is perfect. I've not had a single fault in it. Not bad for an automobile. I wonder how the Indian automobiles compare quality. So, yeah, here's this idea focusing on the big picture. Some of his young employees were encouraged to do that focus on the vision of well getting to Mars or something like that. Here's something else that's little known. Musk is actually fanatic on safety of the passengers in the cars and safety for people. And here are the 50 safest rated cars in the world and model three model S and model X are the three safest cars in the world. How does he do that. He doesn't do it by testing and debugging. He does it by. Okay, there's my 45 minutes. I'll put it on snooze that gives me nine minutes. If I need it, but I won't. Musk hires the smartest safety engineer he can find and says, I don't want you to merely meet the safety standards of California. I want you to design the safest car ever built.  And the ambitious young architects is I want to work for you. I want to design the safest car in the world, and they did it. In other words, they do it. They do it through architecture through design through engineering. They don't debug a bad car after it's rolled off. That's what we are still doing in software. We are testing and debugging that software rather than designing the software to not have bugs in it. That would be called the defect prevention process, which you'll find I've written about. So engineering is complex. Some of you will be a little bit overwhelmed with what I've presented some of you will say this is not for me. I'm going to go back to my coding. Sorry about that. I hope there are a few of you leaders in teaching and in your companies. It said, this is for us. This is an agenda for India. We will lead the world in software engineering. We will take in the into use these ideas before most people outside of India have woken up to the idea you still have a chance. So here's the book I'm working on simple pre copy. There it is. And recently we made an attempt to simplify. We all shall away and I were talking about the iron train triangle and getting very unhappy about it. So we defined a five of the pent up with five notions where we brought in things that are not in the iron triangle like the idea of designs, the idea of quantified values, the idea of efficiency that I talked earlier, and the idea of far more resources than simple money and time. So if you like this is the definitions of all these are right here. But if you like this is my new simplified model of software and systems engineering. And it's quite fresh we invented the whole thing from scratch, just getting angry at iron. Triangles and their comments about the in August this year. So now I'm done with my presentation. Oh, here's another free book. If you absolutely insist. Everybody talks about complex and and complicated systems. And I believe the problem is not that the systems are complex or complicated. I believe we don't have the tools to see and understand them. We put all 100 such tools in a little book called techno scopes, which in fact our engineering tools for looking at the black box and understanding what is inside. So in other words, I do not believe in the theories that of complexity and complication is a problem. The problem is us. We don't have the tools to see complex systems and understand them. So here's my talk. Oops, go back a slide, but these are so here's a reminder we did. And we then do we have a how many more minutes do we have for questions. Go ahead. Yeah, I think it's first of all, thanks a lot. Tom, that was amazing. I didn't realize we ran out of the 45 minutes so quickly. This lasted a little longer. But I'm sure you'll be in the hangout table and, you know, your knowledge is accessible through all the links you've provided greatly appreciate. First of all, I think I'm quite amazed how you've taken care of your stakeholders by putting these QR codes so people can scan and get access to this very easily. I thought that was very thoughtful. You know, that you know other folks can kind of copy. Cool. I think, again, I can, I can go on and talk about everything I got out of this talk, but I think there are a few questions we should get to. So I'll kind of quickly jump straight to it. Tom, if you're okay with that. Yes, go ahead. Cool. I think we could stop sharing your slide so people can see you full screen. The one question I saw it was give me an example of language. Yes, yes, so then to answer the question I need the slide so I move back to one slide. Here is an example of the planning language playing which which I started inventing in my software metrics book 1976. So I've been doing it for about 50 years. This is the language which Intel has adopted, for example. And so here is one requirement of a value. Here is a statement of the ambition level this is what we call the bullshit level it's it's almost the same as user stories by the way. If you go to engineering would say, if define a scale of measure. That's the big trick. And I teach this in my book so here is a defined I don't just say the car is fast I say, we will use miles per hour or kilometers per hour as a scale of measure. And then I say, we will measure it with this speedometer on the car, or maybe the police will measure with a radar system. That's the meter specification. Then who are the stakeholders who care about this United Nations Children's Fund, etc. And what is the status at the moment, we are at 50 on the scale and what is the goal. It's to increase from 50% to at least 95% by 2019 in this case but that was then. Okay, so here is a, here's a practical example of a value or quality requirement using plain which. Now, the, this is also plain which this is the sum of values versus the sum of costs for different architecture. That is plain which here I showed you the simple example using a simple spreadsheet of the small company. They are looking at one design on sprint nine and estimating it will give us 50% of this goal. And they actually achieve 95%. That's the feedback and measurement. This is plain which in that particular example. I showed you a few more impact estimation tables that is playing with so in a way so the end. And then of course, all of the free books I've offered to you, including the competitive engineering book. Yeah, competitive engineering book has a cover that looks like this. Here is the book, and you can, by the way, there is an Indian edition of the competitive engineering book for only 400 rupees or something like that. If you want a paper copy cheap in India, you can get it, but I'm also offering the PDF absolutely free in this set of slides and the, the competitive engineering book is 500 pages with plain which it defines language. So that's the answer to that question. All right. Thanks, Tom. I think we have a few more questions so I'll quickly go over here we have ankit agarwal so ankit is basically saying fascinating talk more than what I was anticipated. This, the question basically here is how does one change the mindset to question owns belief that I may not know everything. Okay, changing mindset is difficult. I've been trying for 50 years and I succeed some places like Intel and unit Packard very mature motivated companies. I also succeeded with my friends at Tata consultancy services. And there's a story about that on the second slide. Okay, so some very smart Indians have received them. But most of the world doesn't know about these methods. They don't try to do the methods they're not motivated. Why not. There's a long answer to this question I'll give the short one. You get people get paid for failure and for delivering bad systems. Why should they change. What if you never got paid, unless it were delivered to the highest quality on time under budget. Maybe you would be motivated to use these methods. Then, if they help you. So, so the long story short, people are not motivated to change to better methods. And the world allows them to use the ridiculously bad agile methods they are currently using and still get paid for it. Somebody has to get smart and stop paying for failures and delays and bad quality. And then people say, but how are we going to get paid and somebody said, Oh, Tom held the talk at agile India and said he thinks he knows the answer. Let's try. And those two have tried my methods like Intel unit Packard Boeing IBM and TCS have succeeded. Awesome. All right. One quick question from me Tom. I think you referred many times in your talk the importance of having, you know, really smart people really good people. You know, I think you also talked about how Musk uses hyper tries to hire the best engineers. What is your advice to anyone who is trying to build a team and is looking for hiring the best people. How, how would you suggest they go about it. I, I think smart people know smart people. And I know India has a hell of a lot of smart people. They're not difficult to find. Okay, now, if you give smart people bad tools, they'll do bad work. One test might be at the interview. You give them my competitive engineering book for free. And you say, come back for a follow on interview and tell me what you think of this book. If they come back and say I think it's great ideas we should do them, then I would recommend you hire the people. If they come back and say this is too difficult. I like scrum or I like safe, then I think they're not smart people and you should not hire them. That's a great litmus test to to figure out who to hire. Appreciate that. I think, by the way, we could, that was a little bit self serving. Hey, give them the must methods book. And if they come back and say I love these must methods, hire them. Sure. Awesome way to recruit people but as he says so that's great. All right, I think what I'll do is we just a little out of time so Tom if you don't mind, we can move over to the hangout table but before we do that I just want to thank all the participants for joining in today. And I want to thank Tom for this wonderful, wonderful insightful talk. I appreciate it. Thank you very much. One thing for people who don't get their questions in. I have an email, Tom at the guild.com. And I invite you. No charge to ask me questions and have discussions. Any time. Be my guest. I'm amazed how quickly Tom responds. Trust me on that.


All right. So tell us who you are and what you're working on. But my name is Dave. I'm a web developer and I've been working on the admin screens for already. All right. Well, let's see them right on. So I'm logged into already here as an administrator and that lights up this admin section here and I can go into campaigns, which gives me a list of all the active campaigns in the system. And I can create new ones here. I can click on them to view some information about it. See the activities for that campaign and then do all the basic things like editing my campaign and deleting the campaign adding new activities. I see. So this is the sort of flow that you did. Yeah. All right. So how hard was it to do?  It's using NBC six. So, you know, we have the standard controllers in the background and we have a entity framework context that we're using to get the data and save it back. So my understanding is that some of the stuff was already there. So what was it that you changed? You told me there were some fundamental changes that you made. Yeah, we changed some of the patterns that we're using. We were running into some issues with the way we were getting the data was sometimes causing problems as opposed to the way we needed. So when we're getting the data just to display it, we needed to do that differently than we were getting the data so that we could make changes to it and save it back. I see. So what we did is we started to separate that out by thinking of it in terms of read only queries. So when we're getting the data, we're using queries and when we're getting the data that way, we're never saving it back. I see. Getting the data to display it on the screen. And then when we're saving the data back, we're using commands. I see. So the commands are more the right portion of the model. I see. Well, let's take a look at some code. Maybe show us how this all works. So let's take a look at the campaign controller. So this is the controller that drives those campaign pages or we're listing them. And you'll notice probably right off the right off the start here is that there's no context coming in here. So my campaign controller doesn't have a dependency on my database context. What it's using is it's using a product called mediator. It's a new package built by Jimmy Bogard. And what that allows us to do is we set send commands on this mediator bus and then we get results from that. So I see very abstractly the controllers thinking in terms of commands or queries that it's sending off to the bus and then just getting the results from that and reacting to Let's see. Let's see the let's see one of the actions where you actually make something. Sure. So let's let's take a look at the index. So the index is where we're listing all the active campaigns. Right. So here what we're doing is we're saying we're sending a campaign list query over to the bus and then that gives us back a list of campaign summary view models which we then pass over to the view. Can we see what the campaign list where it looks like. Yeah. So it's very simple. It actually has nothing in it right now. In the future here we're going to have that scope to tenants organizations in the system. Right now it doesn't actually. So this is really just a POCO that got it is the parameters to the query. So how does a bus know to translate this list query into the DB context select statement. Yeah. So that's that's the interesting part. So that's just the query which is the things you need in order to execute the query. Sure. And it is understood by the handler the query handler which is here we have this campaign list query handler. And really the only connection between the two is that we implement I request handler and there's the that's the tieback. So that's how it knows mediator knows that if I'm executing this type of request. So that's the query type. This campaign was query to run this class and that we're going to return a number of campaigns. So this is like a really loosely coupled way of saying I have this object. Yeah. And I'm going to send this request off. Yeah. And somebody is going to take care of that. And give me back the thing. And the thing that's going to do it is whatever an I request handler is. That's right. And it's going to say OK. If you're an I request handler you're going to have this is the kind of thing I'm working on. And this is the kind of thing I'm returning. And that's what this is doing. And so it automatically sort of glues this all together with dependency injection. Whatever's going on. Yeah. All right. So this is where we're actually taking dependency on our database context. So that gets injected through the D.I. framework and B.C. six. And then when we handle the request this query that's when we're actually executing the we're creating our database here. And then we're using this link projection to project that over to our view model to do a very efficient query. We're not pulling back anything more than what we need. And then returning that back. That's pretty cool. So what would be the main reasoning for doing this type of decoupling. One thing is it makes it super easy to test. So my controller. There's that controller action. Really no point in testing it because there's nothing there. Yeah. If I was testing it the only thing I'd be testing is mediator at that point. So there's no point in doing that. But what we can do is write a test specifically for campaign list query. I see. And then all I need to do is create a new handler pass it in a context of some sort. Maybe it's probably tied to an in memory database instead of an actual SQL server database and then call the handle method and check the results to make sure it's what we expect it to be. Interesting. So the work that you did is you literally took all of this sort of like fetch logic out of the controller action method and you sort of offset it into this sort of mediator pattern. And because we're doing the other really nice thing is that because we know that it's a query and we're only ever getting that data for read only purposes to display it. We can we can really find start fine tuning that query. So one example is something that we should be doing here is as no tracking which is a hint that tells any framework. I'm never going to be changing this. I don't need all the change tracking. I see because usually what's happening is if you change a few change a property what's going to happen is going to say it's going to dirty itself. Yeah. And it's going to say hey I'm dirty. I need to be saved or something's going on. That's pretty. So we can tell it. We don't want to do that in this case because we're just querying it for read only purposes. Let's talk a little bit about sort of when you are actually you are doing it. What does that look like you're still going to use the mediator pattern. You're still going to have some handler I request handler. What does that look like. So let's start by taking a look at the edit command here. So this is the get command the get action method. So here it's a query again. We're getting the campaign summary. So very similar to what we had before. And then we have a few checks here just to make sure that the user actually has rights to edit this before we return it to the view. So that's no different early. That's just passing the data to the view. But then when it comes back that's when it is a little different. So now instead of a query. So these are just our checks here to make sure his user actually allowed to do this. We still have the validation in the in the controller here. And then this is where we're passing this over to the bus. We're saying instead of a query here we're passing in the edit campaign command. So it's a sort of query command pattern. You see in the query you're getting stuff back in the command. You're actually telling it to do something. So here we can look at the payload for this request over to the bus is a campaign summary view model. So that's the data that the user changed. And then when we look at the handler for that one's that's the edit campaign command handler. This is where we go and query for it not without the change tracking this time because we actually do want to edit it. So we have our campaign and we map all our all our properties back from the view model to the the actual EF model class call update on it. Tell any framework update this this entity and then save changes. And I like if you if you scroll up you can see that it's implementing a special interface that does the glue right that tells you what it's returning. Right. It's the same thing I request handler we have this command and then we're going to return this in. Yeah. And in this case what I'm doing is I actually use the same command bit of a cheat but using the same kind to create a new one. So first I checked to see this is there one in the database that matches this idea. If not I'm just creating a new one. And then it passes back the ID. So on my create I can actually I know the idea of the one that was created. That's what comes back and then I can redirect to the details page for that campaign. How long did it take to do this kind of refactoring. It took us a little longer than we thought initially. Just going. It's always a little longer when you're starting with something as opposed to when you're doing it from scratch. But it was about a better party yesterday. There was two or three of us working on it. How did the tool and how did Visual Studio help with all of this. Was there anything that it did that you're like man I couldn't live without this. Well you know it's the intelligence right now. So it even though the only thing that's gluing these together is this Visual Studio knows that in in my campaign controller. So I'm calling bus and bus dot send. It just takes a request. You have no idea what type it is. But as soon as I give it a strongly typed command or query here it knows what the result is. It's telling me that it's a campaign summary view model that's coming back. It's just you know that's Visual Studio. It's the way intelligence lights up and it just guides you through the process. Awesome. Well I guess I'll let you get to work. But all right. Thanks.


What's up everyone? It's your girl, Kenzie here from Leighton Sports Cards and I am ripping 2022 Tops Chrome Formula 1 Racing Hobby 6 box break number 28 random teams. Again, here's a look at the random results. You can always find these at leightonsportscards.com under the results tab. Link also in chat for you. All right. Here we go. Good luck everyone. Let's see a photo variation out of this one. We got a couple golds. We got an orange. Got some huge hits out of the first half of this case. Let's keep it up for the second. Next break we're looking to fill is going to be F1. Same format, random teams. They're going to be eight box breaks. These are the light versions. So again, in the light, there's four way raised parallels per box. That's what we're chasing in those as well as color. There's color way raves that look absolutely nasty. Votos on the checkered flag speed demons of Lewis Hamilton. That's what we're looking for in those a little bit cheaper buy-in as well. Those are only 99.99 spot. Five left in number three, I believe. Lando Norris Refractor. No. Off to a hot start tonight. Baseball. We just have one baseball break going tonight and it is full. Now we're moving on to some iMac basketball. Those are five box case breaks tiered random. You get two teams per spot there. One from the top tier and one from the bottom. Cadwell Refractor. And then in the night with some football, we got some half case spectra pick your teams. Impeccable random teams, random division, Norris and Ricardo Refractor. And then ending the night with a dual mega football case of Impeccable. One first off the line and one hobby. McLaren Refractor. So definitely check those out. Let me know if you have any questions. No personal is going here on the main channel tonight. Forrest is currently live over on drip though, ripping personals. They have purple Fernando Alonzo for Alpine. 366 of 399. So go check him out. So show him some support. It's a new thing that we're trying out. Yuki on the rookie speed demon refractor. Or sorry, technically not a rookie. It's Joe Guan Yu. There he is. Joe Guan Yu rookie refractor. Let me know if you have any questions. Thanks for hanging out. Tunin' in, saying hi. Refractor of Lewis Hamilton, Mercedes. Hope everyone's having a great day. Having a good start to their week. We've got gold and yellow or gold and purple Lewis Hamilton on the award winners. There you go for our Mercedes saying hot this case, Hamilton and Russell. We've got Mosaic basketball release on Wednesday. We'll be ripping that all day Wednesday. Not Aston Martin. We've got breaks up scheduled already. So be sure to check that out. Wednesday daytime, you got kick your team style. So you can pick your favorite team or chase some of those big rookies. Red Bull Refractor and Green of Gunther Steiner for Haas. That is 81 of 99. Lots, lots going on. Lots to look forward to. But yeah, hope everyone's doing well. Refractor Speed Demons, O'Conn. George Russell on the Refractor. And we've got Gold Checkered Flag coming up here. Of Mick Schumacher for Haas, 37 out of 50. Here you go, Haas on the Gold Checkered Flag. Nice. Schumacher Refractor of Sebastian Vettel. Cardo Alonzo, Alonzo and O'Conn. Vettel, Hamilton, Capito and Romero Refractor. Box two. Got a gold out of the first one. Let's see a gold auto. I don't know. We did just pull the gold weight. No, that was the gold weight. We had the true gold. Let's see a true gold auto come out of here. Or a red or a super. I'd take any of the above. Any of the above would be great. Refractor, Ricardo. Yeah, good lineup tonight. Let's get those breaks filled up. Fernando Alonzo. We got another Gold Checkered Flag, another one. That's one rookie. Joke won you. It's a joke kind of case here. Two out of 50. There you go, Alpha Romeo. That is William S. William, staying hot. There you go. Congrats on that one. Mag that one. What a case.  Vershore Refractor. Ricardo Refractor for McLaren. Hamilton. Schumacher and Magnuson. What's up, dogs? What's up, my dog? How's it going? We've got Red Bull Racing. You know who that is, right? Dog the Bounty Hunter? You ever heard? That's not even funny, then. You've never heard of Dog the Bounty Hunter. You've never watched that show go up? No? Oh, man. Alpine. We've got Purple F2 Theo Pouchere for ART Grand Prix 199 of 399. I'm doing good. Starting off hot. Great first break of the night. Continued hot on the second one. Speed Demon Sergio Perez. Really want a super. Got Lando Norse Refractor McLaren. Yeah, Sarah, we really are. No, it's not. No, it's funny. Refractor Sergio Perez, driver of the day. I love watching that show. Green and red, Ricardo. Yeah, that's what you get. That's karma. That's karma. But basically he was like a famous bounty hunter that just goes and tries to pick up these people without standing warrants and stuff. ART Grand Prix. He was just like a really cool guy down to earth. Red Bull Racing and Green F2 Future Stars Marino Sato for Virtuosi 95 of 99. Oh, man. I have no idea. When did that show come out, Sarah? That was a while ago. Latifi and Albon. Was it before 2000? Oh, yeah. Oh, yeah. I'm watching cartoons. McLaren, Refractor, I guess. Okay, how about this one? Lizard Toe Licky or Lizard, Lizard, what is that? Was it Lizard Something? The show where they go around and just tow the cars or mail. I mean, those are like scripted. Lizard Lick, Lizard, something. I can't remember what it is. It was funny though. Future Stars, Checker Flag, F2 Racer, Dennis Howard, Prima, Speed Demons, Alonzo, 2004.  Lizard Lick, Toe. Yes, Sarah knows what I'm talking about. Capito and Refractor, Max Verstappen. Nice one there. All right, box three here. All the MTV, you know which one that has me scarred? It's funny. I think it's called scarred. What's the one that came on super late at night that would always show like the nasty gruesome skateboard injuries? I think it was called scarred, wasn't it? Oh, that was so gross. I still can't watch stuff like that. Do you? That's hilarious. Raider, Room Raider, I don't Refractor. I remember Silent Library. You ever watched that one? Oh my gosh. Purple Checker Flag, Fernando Alonzo, 80 of 199.  Oscar, Pia Stree, Checker Flag, Speed Demons, George Russell. What's up, SE? Yeah, Lance Stroller Refractor. Yeah, I remember that one too, Sarah. That was funny where they like go on those big buses that would go on the big bus and like watch Future Stars, JQs. What's the one where the parents tried to set them up with like these like they did interviews and picked out people they like to try and get them away from their boyfriend or girlfriend they didn't? Verstappen and Perez. That was a funny one too. Man, they used to have good shows back in the day. Don't want you, Mercedes. Yes, I remember. Okay, I love Zoey 101 because of the cash-a-crash. I like cash-a-crash. You like cash-a-crash. Wee, I cash-a-crash too. Chippin' in the morning. Chippin' in the evening. Chippin' at a quarter to three. I don't remember. Max Verstappen, 57 of 399. That was my all-time favorite. Zoey 102 is coming. What? Is it her daughter? That's why they stopped it because she got pregnant. Man, going down memory lane here. Refractor of Alphatari. If Sarah is there, tell her I said hello and then I just shot her a text. Sarah s e underscore one just texted you. Carlos signs Refractor. Flavor of Love. Is that what it was called, dog? That's funny. That is funny. It's not funny. We've got Leclerc on the Refractor. What was the one I was asking Blake the other day if he saw? Because he's your age too. I think he's 22. What was it? It was on Disney Channel. Sergio Perez on the Purple Green and Latifi and Alban. It was I loved Lizzie McGuire. Oh my gosh. That was one of my favorite shows. Haas Refractor. I would watch Dexter at 6 o'clock from 6 to 6.30. Yes. And then I would watch Lizzie McGuire from 6.30 to 7. So I was on Do Not Disturb As A Child from 6 to 7 watching those. I loved it. Red Bull Racing. We've got nice Mini Diamond. Lewis Hamilton. 94 of 299. Mercedes. And the Lizzie McGuire movie. This is what dreams are made of. Hey. I still jam out to that song. And it's funny because Don's never seen high school music. I used to have slumber party sleepovers with all of my friends and we would watch it when it first came out on Disney Channel. Leclerc. High School Musical. That's like a generational movie that every one of this generation has to see. Yeah, yeah, that's fine. Gassley. We've got a True Gold coming here. Sergio Perez. Yes, I see everyone. I know every song. I literally have them on my phone right now. F1 Gold. True Gold of Kevin Magnussen for Haas. That is 42 out of 50. You go Haas doing well this break. Nice. We'll mag that one for you. Parental Control. Yes, that's the one I was talking about. Yes, I know. You know what song I was singing the other day, Sarah? From that, Alexander Alban. We've got an Orange too. F1 Auto of Franz Tasch for Alphatari. There we go. We'll take an Orange Auto of the principal. 13 out of 25. Alphatari. Congrats on that one. That is going to Mark D. There you go, Mark. I want Fabulous. That is my simple request. All things Fabulous. Bigger and better soon. If something expires. Schumacher and Magnussen. Don't get me started. I know like the whole High School Musical. What's it called? You like the Jonas Brothers too. Jonas Brothers? Yes. I am a Joe Bro. My favorite was Joe Jonas. He was my favorite. Everyone always like Nick. No one ever liked Kevin. Sorry, Kevin. But Joe Jonas was my favorite, especially in Camp Rock. Sarah, I know you know Camp Rock. Yes, absolutely. Gasly and Yuki. Same here, dog. Yeah, the music videos. Aston Martin. It's the jealous song, but I don't know who sang it. What on what? It was one of the Jonas Brothers had a song called jealous. Prima Refractor. We've got Dennis Hauger on the Mini Diamond, 293 of 299 for Prima. And your great, great, great granddaughter. It's doing fine. Beauchamp on the checkered flag. You got Speed Demon, Sergio Perez. My favorite Joe Bro song is Love Bug. That's my favorite one. We've got Refractor, Pierre Gasly. Celebrity. No, I don't remember that one. Refractor, Botos, and Joe. They came to Orlando twice, Sarah, and I was so mad because I had nobody to go with. So my fiance is like Ken's. No, I'm not going to a Jonas Brothers concert. McLaren Refractor. And like my nieces probably would have went with me, but like my oldest niece is a sophomore in high school. So like she's not a true Joe Bro. Williams Racing Refractor. And we've got Purple, Daniel Ricardo, that is 330 of 399. They were in Orlando twice and they were in, they were in Tampa. I'm going next time. I'll go by myself. I don't care. I should have the first time. Speed Demon's, Pierre Gasly. So it was Big Time Rush past your age. I don't know who that is. You know Big Time Rush? Is it a band? It was on Nickelodeon. Big Time Rush. Oh my. Nicholas Latifi Refractor.  I guess you can. Big Time Rush is like the boy band after the Jonas Brothers. Like as they can't brought it was Big Time Rush on Nickelodeon. Is that like a beach themed one? No. Refractor Verstappen. They stayed in like the hotel or the luxury hotel. Yeah. It was a spin-off of Sweet Life of Zack and Cody is what it sounds like. That was my show too. I had the biggest crush on those twins. Carlos Sines and LaClaire and Sines Dylan and Cole Sprouse, which leads me into please tell me you've seen the movie Big Daddy. Bryson. Oh my gosh. You don't even have to be that. Oh my gosh. Ferrari Refractor. I have to find it on DVD and bring it to you. You have to watch Big Daddy with Adam Sandler. No.  No. Oh my gosh. I feel so old. Refractor Bochung. He has never seen Big Daddy. Yeah. Sarah says you're in class now. That's your homework. You literally have to go home and watch Big Daddy. It's probably on Netflix, isn't it? And Topanga. I remember that one. Fernando Alonso. Topanga. I watched that. Yeah. Alec Mack was your childhood crush. We've got Ocon Refractor and we've got paint. F1. Max Verstappen for Red Bull. 24 of 75. There you go. Red Bull. Spreading the love. I love to see it. Everyone hitting. We'll mag that one for you. Cutest kid ever. Okay, Toc.  Future Stars. Hip hop. Hip hop. Anonymous.  Give him all the easy ones. Sato Future Stars Refractor and Rookie Refractor Auto. Joe Guanyu. Alpha Romeo. Wow. We had the what? The Gold Wave Auto out of the first half and now a base Refractor Auto. Alpha Romeo. This go around William S. Wow. Wow. Yeah. Dylan and Cole Sprouse Timothy. Wow. This case is bananas. Hip hop. Hip hop. Anonymous. William's Racing Refractor and we've got purple. Checker flag. Joe Guanyu. Why not? 107 of 199. There you go. 30 packets of ketchup. How do you clean up your milk? Just throw a bunch of newspaper over top of it. And okay, how about this one? You're gonna say no. Mr. Deeds. I feel like I'm talking to Hannah. Did you ever meet Hannah who used to work here? She's literally seen like two movies her entire life. But like, she's never seen Forrest Gump. Like, it was no way. I know Forrest Gump, but I never accept that one. I love you, Jenny. My goodness. Haas, we've got a mini diamond Jack Duhan that is 297 of 299. I can't believe it. I feel so old. I've seen holes. I've seen holes too. Everyone's seen holes. And the biggest crush on zero too. Speed Demon's Refractor, Carlos Sines. Okay, like blank check. Is that any of your favorite movies? Yeah, that's what Sarah was saying, dog. We've got Future Star's Refractor of Nassani and a Sergio Perez. I believe this is a photo variation. Give me one second to confirm. Sergio Perez, card 16. Yes, sir. There you go, Red Bull with a photo variation. Who's got Red Bull? Ammo D. There you go, Ammo. Very nice. On the Sergio Perez photo variation. We'll mag this one for you. Water Boy. Yeah, that's a good one. Sarah said, ain't no way. That's the one I was thinking, dog. Laguna, Laguna, Laguna Beach. I remember, I wasn't into those type of shows when I was younger, but I definitely know that one. Sergio Perez, Refractor, Red Bull. Yeah, you have a lot of homework to do, Bryston. Just those two are like original, like Adam Sandler. Esteban O'Conn. Who's your favorite team? The Goddamn Jets. I'm only seeing the grown-ups and... Okay, that's like old Adam Sandler. Gasly and Yuki. Grown-ups and what's on that recent camera? Where he got... He was gambling. He was like a broker. Yeah, I was just talking about that the other day, actually. Carlin on the Refractix, I was talking about KG. Yeah, Kevin. Hustler? Hustler. Oh, no, that's the other one. Gem? Something Gem. Uncut Gems. William's Racing Refractor. We have Purple, Max for Staff and Grand Prix winner, 175 with 3.99. If you get a rare card in the next three packs, you'll donate. All right, let's see. Does this count as one, then? This is the first pack. Let's see. Speed Demons of Albon. Too old? You didn't watch the Amanda Show? Oh, my gosh. Lose Hamilton Refractor. All right, last one. Let's see if 10K will donate if we get a rare card here. Let's see. Let's see. I don't think we have anything super rare coming. Gasly Refractor of Theo Poucher on the ART Grand Prix. I like it. Oh, my gosh. We have... Nice. How about a red and orange? George Russell. There you go, Mercedes. Nice. Orange and red. We've got Vettel and Shrull. It's all good. Appreciate you for hopping in and saying hi. We got Saudi Alphatari Refractor. The Hills, Runtals. I loved Runtals. That was sick. LeClaire and Signs. The Run DMC. The lead rapper for Run DMC used to have a show. My Super Sweet 16. I remember that one. Mercedes Refractor. Pumped was a fun one, too. Cribs. Yeah, I liked it. Man. We've got Ferrari Refractor. This is F1, but the first couple hours of our stream are going to be F1 breaks. We've got Verstappen on the checker flag and Speed Demon's Refractor of Vettel. After this, we have a couple of the Lightbox breaks, half cases. And then after that, we got Baseball, Basketball, and Football. And Sato on the Refractor F2. He really was the big bubble bath going on with some words of advice. You know what I've heard on the radio? The other day when I was driving to work, I was listening to the Breakfast Club. And like, I'm wishy-washy with Charlemagne. I don't know if I like him or not. I mean, he literally makes a living making fun of people and judging people, but whatever. He said, always try to be a nice person. But sometimes you have to share it. Always try and be a good person. But sometimes you got to change who you're good to. It's very true. Very true. Asked the Martin Refractor. I was like, okay, Charlemagne. And I also agree with him. Like Uncle Char says, craziest people come from all of Florida and the Bronx. McLaren Refractor. And we've got Purple, Beauchamp, 186 of 399. More than half the time, Donkey of the Day is coming from Florida Man, arrested for. Good old Florida. Speed Demon Refractor, Max for Stappin'. Yep, yep, yep. Got Speed Demon's Lando Norse Refractor. Come on, we need an auto. Let me see, what, one auto? No, we had two autos, I believe. We got a Gold Wave coming. Drugovich, feature stars, Refractor. Two autos. Two autos, Gold Wave, F1 racer of Matia Bonito, principle for Ferrari. That is 22 out of 50. You go Ferrari. They really do. They really do. Oh my gosh, another one, literally. We've got Refractor Botos and we've got Auto. Yuki Sonoda, Alphatari. There you go. Alphatari is Mark D. There you go, Mark. Very nice. We'll mag this one for you. We did, dog. I'm telling you, I feel like TV nowadays is like so boring or just cliche stuff. Hamilton and Russell. Yeah, that's true. That's because now you've got kids toddlers and stuff that they don't go outside. They need to go touch some grass. They just sit inside all day on their tablets. Williams Racing Refractor. Yeah, outside playing. See, you can't blame me for that. I felt outside playing. Prima Racing Refractor.  We've got Future Stars, Mini Diamond, Marcus Armstrong, 298 of 299. You're just born in a different time, Bryson. First stop, Interfactor. What year were you born? Yeah, we have Checker Flag, Daniel Ricardo for McLaurin and Speed Demon's Lance Stroll. I didn't get my first phone until I was in middle school and it was a hot pink razor. That was my first phone. Yuki, now there's like second graders with iPhones. Magnuson Refractor for Haas. I used to work at an elementary school before I started working here. You'd see kids at the end of the day just walking around with their iPhones out. I'm like, oh my gosh. Future Stars Refractor of Novelac for MP Motorsport. I used to have a phone but it never used to be on. So it was basically like Quaintness to have the phone. Play Snake on it. We've got Alonso and Ocon. A few packs left here. See you guys. Come on, Joe. Born you. We've got a Yuki Refractor. Outside, right? That's like saying the water is gross. We've got Purple and Green Lando Norris for McLaurin, Botos and Joe. We've got Aston Martin. We've got Shawn's question. Last pack, huh? We've got Shawn's question. Yeah. He won't know anything. All those signs. We've got Ferrari and last one we've got Purple Checkered Flag, Lewis Hamilton. There you go, Mercedes. 73 of 199. Very nice. All right, give me one second. We'll do a quick recap here. Man, these mag stacks have been crazy today. Oh, you don't have to mag that one. All right, we've got Green Siner for Haas. Green Future Stars Sato Virtuosi. Gold Checkered Flag of Mick Schumacher for Haas. Our mags. We had the Photo Variation Sergio Perez for Red Bull. The Mini Diamond, Lewis Hamilton to 299, Mercedes. The Pink, Max Verstappen for Red Bull out of 75. A Gold Rookie Checkered Flag, Joe Guanyou, Alpha Romeo. The True Gold Kevin Magnussen for Haas. The Joe Guanyou Refractor Rookie Auto for Alpha Romeo. The Orange Auto of Franz Tost for Alpha Tari to 25. The Gold Wave of Mattia Benito for Ferrari and then the Refractor Auto Yuki Sonota. That'll do it for F1 Hobbies. We've got F1 Lights coming up shortly. Thanks, everyone.


On page 41, we add left hand chords into the song. Notice that you have a lot of B-flats in the chords in your left hand. Don't miss the B-flats. This is Evening Song.


Now, as gunshots echo across the windswept snow-covered reaches of the wild northwest, Quaker puffed wheat, and Quaker puffed rice, the breakfast cereal shot from guns, present the challenge of the Yukon. It's Yukon King, swiftness and strongest lead dog of the northwest, placing the trail for Sergeant Preston of the northwest mounted police in his relentless pursuit of lawbreakers. One King, one Huskies. Gold, gold discovered in the Yukon, a stampede to the Klondike in the wild race for riches. Back to the days of the gold rush, with Quaker puffed wheat and Quaker puffed rice bringing you the adventures of Sergeant Preston and his wonder dog Yukon King, as they meet the challenge of the Yukon. Fellows and girls, picture yourself dog sledding hour after hour on the Yukon trail, like Sergeant Preston. You'd soon find out that real stamina calls for a nourishing He-Man breakfast.  For a nourishing treat, eat Quaker puffed rice and Quaker puffed wheat. Jeremy Ward operated a freight line between Whitehorse and Dawson. A sturdy building in Whitehorse served as both a home and office. Old Hank, a retired dog driver, was Jeremy's closest friend and frequently came into town to visit Jeremy and Jeremy's grandson, an orphan named Billy.  Billy Wide-Eyed and old Hank sat at the front window. Hank was in the midst of one of his fabulous stories of the trail while Jeremy worked on records and in a room. The walls were coming at you on the trail? Yes, sir, ten of them. Well, there I was. Oh, Grape is interrupted again. Yes, you dog team coming this way. Jeremy, I told you I'd let you know when I saw that messenger. What makes him so all fired important? I declare I never saw a so squirmy. Well, Hank, I didn't want to say anything before, but I can tell you now, that messenger is coming from Diamond Bill Davis. From Diamond Bill, you say? Yes, he's a collector of jewels. He thinks he's like Diamond Jim Brady. He brought a fortune in diamonds with him when he came from the states. There was a piece of the paper about Diamond Bill. Said he was going to ship a million dollars worth of diamonds back to the states. He's going to sell them there. It was a fool idea to put that in a paper. It's an invite to every crook in the Yukon. Is he really sending down a million dollars worth of diamonds? Well, that's stretching it, but he's sending a lot. People around here don't have much use for fancy jewelry and diamonds. He'll get a better price for the jewels in the states. Hi, Sarri. Are you going to handle the shipment? I'm to see that the diamonds get as far as dorshing. After that, it's up to the steamship company. Those diamonds would make a big haul for cro- And that's why the shipping plans are mighty secret. No one knows how the diamonds are going to be sent to dorshing, nor when, not even me. You don't know? Nope. The man I'm expecting from Mr. Davis will bring word about when and how we handle the cargo. Now, you keep watching out that window. Let me know as soon as you see a man with a dog. I told you I'd let you know. You're watching, Grandpa.  All right, but just keep watching, that's all. I hope he doesn't interrupt us again. Now, well, where was I at? You were out of ammunition, and the wolves were closing in. Oh, yes, yes, that's right. Twenty wolves. Ten wolves. Oh, ten, huh? Well, there I was, with ten hungry wolves showing their fangs. I expected them to finish me off most any second. Then I heard a man yelling in the distance. Get him, King, he yelled. Get him, King, just like that. Then what? Well, then I saw a great big dog streaking across the snow. He was coming like grease lightning. Well, you con, King. Sure enough. And he lit into that pack of wolves, frightened, tearing and dashing and leaping. I tell you, I'd never seen the like of it. Then Sergeant Preston with his dog team comes into view. He's coming fast and shooting with a gun in each hand. Then those wolves, they just skedaddled. They got out of there in a hurry. Si, there comes a man with a dog team. Maybe that's the messenger Grant is waiting for. Sure enough. Jeremy! Jeremy! Here comes the messenger, the man you're waiting for. Good, good, good. My golly, I'm glad he's here at last. Jeremy, water around? Yeah, that's my name. Come in here, come in fast, I'm waiting for you. I have a letter for you. I know what you have. I had a hard time on the trail. I was delayed a little bit. That's all right. You were here at last. You didn't tie your dog. Now they'll say where they are. All right for a minute or so. Where's that letter? Get the letter right here, Mr. Ward. Yeah, bring it in my office. Hank, you'd better come along. All right, Jeremy. Mister, do you mind if I go out and look at your dog? Oh, I know. No, go ahead, sir. Billy, if you're going out, see that you pull on your pocket. Oh, yes, sir. Let's get back to my office. I'm down right there. You should see what that letter has to say. The messenger and old Hank followed Jeremy into the office. Billy hurriedly pulled on his parker and then went outside to admire the messenger's dog team. The boy was particularly impressed by a strong, powerful lead dog. He bent and stroked the animal's ears. The 10-year-old boy admired the other dogs and then moved to a position behind the sled and stood on the runners. Golly, now I feel just like Sergeant Preston. The game of make-believe appealed to Billy. He fancied himself as a brave malty who maintained law and order in the Yukon territory. He whispered, Come on, King. Come on, King. Come on, King. Come on, King. Come on, King.  Then, growing more bold, he picked up the whip and in a louder voice said, Come on, King.  Dogs became more alert. The leader turned back and looked inquiringly at Billy as he waved the whip and stood on the runners. Bolder then, the boy raised his voice and shouted as he cracked the whip. Come on, King.  Dogs took off with a fast clip and the others pulled their weight. Billy tried to jump off the sled, but found that the lacing of his boots had become tangled with the jagged saw teeth of the brake. He was caught. He dropped the whip and clung desperately to the handle so he would not be thrown and dragged. His cries brought Jeremy to the door with Hank and the messenger close behind. It's your dog team and your sled. They're running away with Billy. Come back here. Come back. Come back here. They can't hear you now. They've gone too far. We've got to get after it. But how? We can't travel on foot. We've got to find another team. By the time we get dogs lined up and get to a sled, those kids will have Billy half way to the body. I'll see what I can find. Billy was gripped by a paralyzing fear. The dog soon left the regular trail and dashed across uneven ground. Billy clung desperately to the back of the pitching, swaying sled, and then his hands became numb. He was thrown off the sled and landed in the thicket by the trailer. His head struck the side of a huge rock. For a time he lay unconscious. He recovered in the shelter of the rock and underbrush. But he was only half conscious when he heard the voices of two men from the opposite side of the massive boulder. Can you open that old man's safe? Jeremy Ward? That's easy. Well, then we've got nothing to worry about. Just open her up and get that letter. But, Baxter, are you sure Ward will have the letter in his safe? Well, of course he will, Slick. Where else would he keep it? But when Ward finds the letter's gone, he'll think back to the people who worked for him who knew about his safe. And he'll think of me. I'll be the first one suspect. No, he won't. Besides that, when he finds the letter's gone, he'll know there's a plan afoot to steal the Davis diamonds. Then the shipping plans will be changed. I figured all that out, Slick. Yeah? When you steal a letter, take whatever cash is in the safe. We use that to frame someone for the robbery. Well, let's hear some more. Who do we frame? My old Hank. But he's Jeremy Ward's best friend. Yeah, he knows all about Ward's business. He probably knows how to open Ward's safe. Oh, I see. Now, Hank lives in a shack between here and town. We'll make a copy of the plans for shipping the diamonds. Then we'll hide the letter in the stolen cash in Hank's house. Then what? As soon as we have the stuff planted in Hank's house, we'll find some way to get Hank out of the way. So it'll look like an accident. After he's dead, the constable will go through his possessions. Then they'll find the stolen cash and the letter. You think Ward'll believe his old friend turned crook? What else can he believe? He'll figure no one else has seen the shipping plans with the diamonds, so there'll be no reason to change the plans. Baxter, that's downright smart planning. Once we know how and when the diamonds are to be sent to Dawson... We can figure a way to get them. This will be the biggest jewel robbery the Yukon's ever seen. We'd better start for town now. It'll be dark when we get there. Hey, wait. If anyone sees me in town there, likely to put two and two together. Remember that I work for Jeremy, that I might know how to open his safe. It won't be hard for you to keep out of sight. We'd stay away from the regular trail. Now, let's get started. Billy's head hurt terribly, but he'd been afraid to stir for fear the man who plotted against his grandma would discover him on the opposite side of the big rock. He sobbed softly as the two men moved away. Who's crooks? Who's dirty, scheming crooks? When he tried to stand, Billy felt as though the world were spinning. His head throbbed where he had struck it on the rock, and then he seemed to see a million lights. An instant later, he slumped to the ground, unconscious for a second time. By the time old Hank, Jeremy and Dave the messenger had found a sled and snowshoes to go in search of Billy, snow had began to fall. This and a high wind soon wiped out the trail. Then darkness came, but the three kept on. In the meantime, Billy regained consciousness on a bunk inside a cabin. He looked up, and by the light of an oil lamp there was a man whose face wore a look of anxiety. The man wore a parka that concealed his uniform. Billy didn't know that he was Sergeant Preston. You must be one of them. We'll take it easy, son. Don't try to talk until you feel stronger. Where am I? In a cabin. I found you in the woods and brought you here. You've been unconscious for a long time. You're one of them. I heard you talking.  Which one are you? Slicker or Baxter? Slick. Baxter, I'm neither one of those men. You are. You must be or you wouldn't have found me here.  I found you unconscious beside a big rock. I put you on my sled and brought you here.  Now tell me, son, what's your name? My... my name? My... oh. Easy. Unconscious again. Boy's badly hurt. I wonder who he is and what he heard. A robbery and a murder. We'll continue our adventure in just a moment. Hey, what's up? Who's on the warpath? Oh, warpath. Me, Barry Hatchet. What goes on? Me now, big chief. Make salvation. Oh, I see. Congratulations are in order. And say I have something I'd like to give you because it's just what a big chief ought to have for breakfast every morning. Must be special big for big chiefs. Oh, it is. Everything about Quakerpuffed wheat and Quakerpuffed rice is big. Take a look at the big red and blue packages. Ah, me like colors red and blue. And did you ever see any cereal so deliciously big and crisp as Quakerpuffed wheat and Quakerpuffed rice? Plenty big. Yes, those choice premium kernels of wheat and rice shot from guns are actually exploded up to eight times normal size. Big chief, like them big.  They're shot from guns to make them crisp and tender, bigger and better tasting. There's bang-up nut-like flavor in every big, luscious mouthful. Me want heat big bowlful now. Coming up, big chief. Quakerpuffed wheat and Quakerpuffed rice are ready to serve. We just top them with milk or cream and fruit and then go to it. And as all you fellas and girls know, you can always have those second and third helpings because Quakerpuffed wheat and rice are so good for you. They both furnish added food values of restored natural grain amounts of vitamin B1, niacin and iron.  Shot from gun. Now to continue. Jeremy Ward was assisted by his old friend Hank and a messenger named Dave in searching for his 10-year-old grandson who had been carried off on a sled by a runaway dog team. The three beat through the wind and snow in the Yukon night, not knowing that Sergeant Preston had found Billy and that at that very moment the boy lay unconscious in old Hank's cabin. Meanwhile, Slick and Baxter crept toward the rear of the building that served Jeremy Ward as a home and an office. There's no lights in there, Slick. I think the old man's going to bed this early. Well, unless he changed his way of living, more likely is it one of the cafes down the street. Yeah. And here we are. Just like old Ward never locks a door. This is going to be a pushover. Better close the door. The safe is right over here. Keep close to me. I've got a hunk of candle here. I'll let it. If we're not disturbed, we can copy the letter right here. Then take the original and the cash to old Hank's cabin. In the meantime, in old Hank's cabin, Sergeant Preston had become increasingly concerned by the prolonged unconsciousness of Billy. Finally, he opened the door and called. King, come in here, boy. That's it, fella. King, I think we better not try to move the boy. We may have a fractured skull. You're going to write a note, King. You're going to take it into town. I'll tell you it's your collar in plain sight. And whoever sees it will take it to the doctor. You'll bring him here, boy. There. Hold still, fella. Just fasten this to your collar. I hope you know what I'm talking about, King. Town. Understand? Town. All right, boy. Good going, King, to town. Good boy, he knew what I meant. The great dog Yukon King, racing toward town, passed two men headed in the opposite direction, but he paid no attention to them. He was intent on carrying out his master's orders. The men were slick and vaxed her. They were on their way to old Hank's cabin, and they carried a sum of money from Jeremy Ward's safe. Also a letter they had carefully copied by candlelight. In the dim light, they could see a Parker-covered figure and dogs outside the cabin. Looks like old Hank's got himself a team of dogs. Yeah, likewise a sled. Seems to be staking him out for the night. It takes care of one thing I was worried about. Yeah, what's that? I was afraid Hank might have an alibi. Wouldn't do to try to frame him for something that happened this evening if he was spending the time with Jeremy Ward. We needn't worry about that now. There he goes inside.  We'll go and jump him now. I don't hang it a waste any time. We'll go and jump him now. Sergeant Preston had been outside attending to the dogs. Before he removed his Parker, he crossed the dimly lit room and bent over the bunk to examine the boy. He found Billy's pulse more regular and his breathing more natural. Then Billy's eyelids fluttered and his lips moved slowly. Sergeant Preston bent low, straining to catch any word the boy might utter. He was so intent that he didn't hear the barely perceptible sound of the door opening. When he noticed a draft of wind, he started to turn. Then the door flew wide and two men leaped across the room. Get him, Slick! Right! The barrel of Slick's gun came down on Sergeant Preston's head with stunning force. Yeah, that did it. He backs to look. That's not old Hank. Sure enough. We'll see who it is. Look there. There's a kid on the bunk. You're sure this is the right cabin? You're sure Hank has moved? Great Scott! Look what's beneath the Parker. A red coat. Baxter's a Mountie. Look who it is. Sergeant Preston. This is a fine kettle of fish. Not what we do. I'll see if he's alive. I didn't hit him hard enough to kill. Besides the hood of the Parker took up some of the blow. He's alive all right. Baxter, what's he doing here? What do I know? The point is, the Mountie is here and we've slugged him. How are we going to count for that? I don't know. But we'd better tie him before he comes too. Well, there's some rope. I'll cut off a hunt. After that crack I gave him, he'll be out for a long time. But I'll tie his wrists together just the same. Hey, close that door. Right. Now here's the rope. Leave him face up so we can see if he comes too. Be sure you take his gun. I'll see about the kid on the bunk. What's the matter with him, Baxter? Is he sleeping? Now he's awake and looking at us.  Who is this kid? Do you know Slick? I think he's Ward's grandson. I heard some talk about him before I got fired. His folks died in the States and he was to come up and live with Jeremy. Is that right, kid? Yes, that's right. And if you think you can get away with robbing my grandfather and murdering old Hansen... What's that? I heard you talking about it. I know what you're going to do. You're mistaken, kid. Maybe you misunderstood something that was said. I'm not mistaken. You want to steal some diamonds, but you had to find out how they were being shipped. You had to get a letter from Grandpa Safe so you know where to steal them. Well, you don't say.  What are you doing here in Hank's house? I said, what are you doing here? I don't know how I got here. Listen, Baxter, we've got no choice. The kid knows too much. You're not getting up. This blows all our plans sky high. Did you get that Mountie's hands tight tight? Sure thing. Here's a hunk of rope. You better tie the kid while we decide what we're going to do. That's a good idea. Sergeant Preston had regained his senses to find that his hands were tied together at the wrist. He had remained limp with his eyes closed, feigning unconsciousness in the hope of learning the reason for the sudden attack. His hopes had been fulfilled when Billy told the outlaws what he knew. Now he struggled at the rope, straining, trying to get his hands free. He raged inwardly at the thought of Billy being roughly handled and tied in his injured condition. His anger added to his strength, but not enough to stretch or break the stout cord. I thought it over, Slick. The Mountie and the kid have got to die. Killing a Mountie is bad business. Preston came here by his own accord. He's the one who lit that candle. The shack is dry enough to burn like tinder. All we've got to do is drop the candle in the box of kindling wood. No, no, I can't do this. Do you think you can stab us? We'll take that chance. Put the Mountie on that other bunk, so it'll look like he was sleeping when the place caught fire. You take his feet and I'll take his shoulders. Maybe after the fire is out, there'll be evidence to show that his hands were tied. What'll we do about that? I'll take care of that. As soon as the fire is going, we'll drop the kid the same. Get his feet. Sergeant Preston remained limp as he was lifted off the floor, but his mind was racing madly.  Put him right on his back so he can cut the rope that holds his wrist. Slick was bent over the foot of the bunk as he lowered the Mountie. Then Preston acted with lightning speed. He drew up his knees and shot both feet out. Then Slick's chin was stunning force. Slick's head snapped back. He staggered and fell. Baxter was wide-eyed with surprise. Before he could go for his gun, Preston rolled off the bunk landing cat-like on his hands and feet. He leaped from the crouch and charred.  Then Preston brought up both fists tied together. The uppercut was short, but full of force. Take it! I'll kill you for that. Then the Mountie's hands came down with a chopping stroke to the wrist. Slick had been stunned but momentarily. When he showed signs of recovery and began fumbling for his gun, Billy shrill the warning. Preston dropped to the floor, scooped up Baxter's gun and fired. The bullet caught Slick and the wrist just as his gun cleared the holster. That does it. Hold it, Baxter. Are you surprised? Stand right where you are, Baxter and keep your hands above the shoulders. That's the same, properly played.  That's seriously. That's King, Billy. I sent him for a doctor. Get over there, Baxter, beside your friend. Come on in. Come on in, all of you. Let's go. Oh, great decision of your right. What's going on here? Who are these critters? A couple of crooks have planned to rob your safe and put the blame on Hank. Doctor, take a look at Billy. He had a hard wrap on the head. He's tied. They're both tied. We're lucky to be alive. I'll take care of that. Preston and Billy were quickly untied. Doc looked at the boy and found that his injury was not serious while Preston searched Slick and Baxter. He found money from Jeremy Ward's safe, also the secret shipping orders and a copy of those orders. Meanwhile, Jeremy told about the runaway dog team and the search for Billy. After meeting around in the night for some time, we decided to go back to town and get more men to help search. We were there when we saw your big dog racing to town with a note tied to his collar. We figured the boy might be Billy, so we came here. You didn't even know your safe had been robbed. No, but this letter and the cash, you'll prove it. Slick, I told you to stay out of town. Now, by thunder, you can go to jail. It was all Baxter's ideas. You'll both go to jail. About the diamonds, sir. I'd impress him. According to this letter, they're supposed to arrive tomorrow. The messenger is going to give them to me and help me plan on getting them to Dawson. That's right, Jeremy. I was on my way to your place when I found Billy. You? Yes, I have the diamonds. They were in a belt under my shirt. What's that? The mounting handle. You were closer to them than you thought. Of all our rotten luck. I'll send them to town and put them in jail, boy. Well, Billy, I have told you plenty of stories about Sergeant Preston and Yukon King. No, Hank, I just, I can tell a story. Can I, Sergeant Preston? Indeed you can, Billy. And be sure to tell how foolish and dejected outlaws look when they come to the end of the trail and their case is closed. In just a moment, Sergeant Preston will give you a preview of today's adventure. Say, fellas and girls, are you building the exciting Yukon Trail at your house? Well, hurry. The Sergeant Preston Yukon Trail cut-out models come with eight different packages of delicious, nourishing, Quaker Pop wheat and Quaker Pop rice. You'll want the complete set, so you'll have all 59 of these larger, easier-to-build models. Just go to your grocers. There's no waiting, no box stops, no coupons. It's thrilling to have models of the very places that you hear about in these danger-packed adventures of Sergeant Preston and King. You get models of the Northwest Mounted Police Headquarters, a lumber camp, mining camp, the White Horse Hotel, general store and jail. You get dog sleds, teams of huskies, all kinds of Yukon animals. You get the Yukon Queen riverboat with a paddle that actually turns. These models are so amazingly different, you even get scenery and the interiors of buildings. So build your complete Yukon Trail from White Horse to Dawson City right away. Get them at your grocers now. They come only with the big red and blue packages of delicious, nourishing Quaker Pop wheat Quaker Pop rice. Yes, the original crisp fresh shot from gun cereal that is never sold in bags or bulk. Listen Friday when Sergeant Preston and Yukon King meet the challenge of the Yukon in the case of the man who fled. A fugitive from justice who had come to the Yukon under a false identity. A sinister blackmailer who met a well-deserved fate and a name scrolled on the wall. Those were the clues I had to work with. They led me to the solution of the murder case but when I found the guilty party I also found myself facing a loaded six gun. Be sure to hear this exciting adventure Friday. These radio dramas, a feature of the challenge of the Yukon Incorporated are created by George W. Trendl produced by Trendl Campbell Enterprises and directed by Fred Flower Day. Today's adventure was written by Fran Striker. The part of Sergeant Preston is played by Paul Sutton. They are brought to you every Monday, Wednesday and Friday at the same time by Quaker Pop Wheat and Quaker Pop Rice. The breakfast cereal shot from gun. Remember for delicious hot breakfast enjoy Quaker Oats. The giant of the cereal is Quaker Oats. Delicious, nutritious makes you feel ambitious. The giant of the cereal is Quaker Oats. And here's why Quaker Oats is called the giant of the cereals. There's more growth more endurance in oatmeal than any other whole grain cereal. So make your hot breakfast nourishing Quaker Oats. Quaker and Mother's Oats are the same. This is Jay Michael wishing you goodbye, good luck and good health from Quaker Pop Wheat and Quaker Pop Rice. So long. This is ABC, the American Broadcasting Company.


Welcome to our lecture on determining sample size when making inferences. Here's an issue we haven't really talked about much up until this point. How do we know how large a sample to take? When we're making inferences about mu, we're using the sample mean x-bar as a point estimator of mu. The sample size is n, but how large should n be? One thing we know is that as n goes up, the size of the interval shrinks by a factor of the square root of n. So if we know beforehand what our precision is, which we've been calling margin of error, if we know beforehand before we start what we want the half-width of the confidence interval to be, or at least what it should be at a maximum, not more than, then we can pretty well figure everything else out. We know v because we know what confidence level we want. Sigma would have to be known for this exercise, so either it is known or we have some really, really good guesses based on previous studies. E is known, that's the precision or the margin of error or the half-width of the interval we're calling it E. So the only thing left is to solve for n, and that's just algebra. An x-bar doesn't count because that's at the center, and it doesn't go into precision at all. X-bars in the center, we have a little bit on one side and a little bit on the other side. Here it is. We use E in order to solve for n. E is precision or margin of error, and it's equal to z times sigma divided by the square root of n. And when we turn everything around, we have the square root of n all by itself on the left side of the equation as equal to z times sigma divided by E. To solve for n, we need to square everything on both sides. So n turns out being equal to z squared times sigma squared divided by E squared, and now we can solve for n. So here's a simple problem. Suppose we know that sigma, remember that's the population standard deviation. We know that it's 20 based on previous studies. We want to estimate the population mean. That's called, you know, confidence interval. We're going to construct. We want to be within plus and minus 10 of its true value. Those who want the margin of error to be 10 on both sides. Okay. And we're going to use alpha rule 5. So 95 percent confidence interval. What sample size should we take? You see the formula now, remember, z is 1.96, sigma is 20, right? The E, the precision, we said 10, that's what we're given. So we just do n equals 1.96 squared times 20 squared over 10 squared. It works out to be 15.4. This tells us that we need to sample size of at least 15.4. That's called 16. So we want n to be 16. And that'll give us the margin of error that we wanted of 10. And those E will be 10. So we finally calculate x bar. That should give us a margin of error of 10. So this one, this problem is, again, sample size determination, but for proportion. When working with a proportion, the formula is very similar. Notice it's z squared. But here we have p times 1 minus p over the precision that we want E squared. Now, again, we don't have a p to use. So we generally assume the worst case scenario that will blow it up as large as it can, which means p is 0.5. If p is 0.5, that'll give you the largest possible n to use. So that's what we're going to do. Well, and it's probably a political poll. The pollster doesn't want the margin of error to be more than 1 percent with 95 percent confidence interval. Right? So the variance using the highest possible p is 0.5. We pretend that p is 0.5. It may not be that, but that's, we take the worst case scenario. All right? So now we take the z value of 1.96. And that's 95 percent confidence. n equals 1.96 squared times what's telling p is the worst case scenario is 0.5. 0.5 times 1 minus 0.5. And the precision that we want it is 0.01, 1 percent. We want to be within 1 percent with 95 percent confidence. So 0.01 squared, that's the denominator. You do the arithmetic. That means you need a sample size of 9,604. That may be a large sample, but that will give you, that's in the worst case scenario. So that'll give you the precision that you want, that you'll be within 1 percent of the, of the true, and there's only one true population proportion, the true p. Now, those of you who know anything about polling, you'll see most pollsters work with sample sizes of 1,000. Why? Well, it's the problem that we had before, but let's make the precision 3 percent, that we don't mind having a margin of error of 3 percent. All right? So now I'll do the same problem. n equals 1.96 squared times 0.5 times 1 minus 0.5 over 0.03 squared. Now we get an n of 1,067. And indeed, that's the sample size that most pollsters work with, because you know the margin of error ends up being around 3 percent, maybe less sometimes, but you know, roughly 3 percent. And that's why most polls, most marketing research studies, you'll find you need a sample of 1,000. And it's surprising that the United States with 310 million people need a good sample size of most things for 1,000. That's all you need. So the next time, you read an article in the paper about a political poll and it says something like about 1,000 people were surveyed for this poll. You know why?