Great ideas repeat. The “correlation matrix” represents an intuitive idea that shows up in many design and problem-solving methodologies. Put this great concept to work for your team.

Good things transcend language, culture, time, and claims to fame. One such concept has cropped up in my career repeatedly, and I find that it truly does facilitate great power to solve problems in brilliant ways. Strangely, the only name I know for it is “Technical Correlation Matrix,” though that name is a poor title for what the idea has to offer.

The correlation matrix is a comparison of needs, requirements, or functions whereby the user identifies a relationship of either mutual benefit, conflict, or no relationship. I have encountered it in Value Engineering, Design for Six Sigma, Axiomatic Design, Outcome Driven Innovation, TRIZ Theory of Creative Problem Solving, Quality Function Deployment (from where the title “Correlation Matrix” comes), and it shows up either by serendipity or through intent throughout the history of invention and engineering design. It is the concept that shows up repeatedly, not the matrix tool specifically.

For example, let’s say that we are designing a backpack for long trips, carrying camping, or mountaineering equipment. It needs to be comfortable, durable, meet certain volume needs, and hit a certain cost target. The category of comfort involves two factors: It must transfer or distribute the load, and lighter is better as an element for making the sale (though, in truth, the pack itself is only a miniscule fraction of the weight of the fully loaded system).

The correlation matrix might look something like this:

Figure 1: Example Backpack Correlation Matrix

In the figure above, the needs or requirements on the left are compared to the same ones on the top. We use a “-“to identify when optimizing the criteria on the left conflicts with optimizing the criteria on the top, and a “+” when optimizing the one on the left aids in optimizing the one on top. A “0” means that optimizing the one on the left produces no meaningful impact on the top criteria.

You will note that I have made the table a little more complex than the reader might have seen in the past, but I’ll bet that most of us have seen this idea before. Why then, if we have all seen it, should I be making such a big deal over it?

The fact that we have all encountered it sometime before should be a clue that it can be a very useful idea; otherwise it wouldn’t show up so repeatedly. This very simple matrix, which takes only a few minutes to assemble (I drew this one up from scratch and populated it in about 3 minutes), can also reveal some very important design or problem-solving opportunities, if we learn how to see them.

Most of us only take a cursory look at the table. We recognize that we can meet our cost target without really jeopardizing any other design criteria. We see that our efforts to increase durability and our efforts to make it a more durable design are likely to work cooperatively. We see that efforts to make it more durable will conflict with our desire to make it lighter in weight. So what’s the big deal?

If that is all we get out of the matrix, then yes, it can be a waste of time to build a table full of “+” and “-“ symbols. That is probably why so many of us have seen the concept, but we don’t make a concerted effort to use it. If it is such a useful tool, then what are we missing?

What many of us miss are the opportunities the tool and the thought process that goes with it reveals. When we examine it properly, the tool and method reveal where we have opportunities to develop a truly innovative and original or powerful solution, above and beyond the regular or obvious.

It is obvious that more durable materials and load transfer systems will cost more and weigh more. What is brilliant is when we can create a more durable and comfortable system that costs less and weighs less. There is a reason I picked that particular piece of the matrix, but let’s get there with a little more explanation of the tool and what it shows.

Notice that I doubled the matrix from what many of us might have seen before. Typically, when the correlation is constructed it looks more like a triangle, like the portion above the grey blocks. However, sometimes the relationship is not the same in both directions when we ask how does one affect the other?

Take the cost factor for example. There is no real reason why, in this example, meeting our cost target would cause us to forfeit any one of the other criteria. The top row of the matrix is all “0” for no relationship. However, if we try to optimize load transfer or durability, we could find ourselves designing elements or selecting materials contrary to our ability to meet the cost target. In other words, driving cost will not necessarily impede durability or load transfer, but driving load transfer or durability to an optimal level could impede our ability to meet a cost target.

That is why I gave an example where we built the matrix one-way and we compared both sides of each relationship. It can be more revealing. Also take a look at the cell comparing Lower Weight vs. Cost Target. To some degree, selecting lower weight materials also means selecting less costly materials. However, at some point, lower weight materials or design elements that allow us to lower the system’s weight might, be more expensive or more difficult and costly to manufacture. Hence we got a “+/-“ in the cell.

We can be a little more sophisticated with the tool, but where’s the magic? Most of what we have discussed is still rather intuitive. Why build the matrix at all?

The matrix can help us find the opportunities to build a revolutionary design. Start by looking for the complementary elements. In our case, it happens to be Transfer Load and Increase Durability.

Don’t stop the examination there, though. Also look for the criteria with which both of them conflict. In our case, it is Lower Weight and Cost Target. Here is the golden opportunity. As a design team, ask this: “How can we leverage the complementary elements of Transfer Load and Increase Durability to also benefit Lower Weight and Cost Target?”

The golden question that shows up in Axiomatic Design, Value Engineering, Design for Six Sigma, TRIZ, and throughout history is, “How can I use this to also do that?” Our truly innovative designs and revolutionary solutions all get our attention because they have brilliantly elegant ways of addressing obvious conflicts. If we did design a rugged and comfortable backpack that was also lightweight and cost effective, we would have a design that we could boast about.

I’ll give you another reason to build the matrix before I go into why the question is important. Take a look at Transfer Load versus Volume Target. Notice that meeting a large volume target conceivably makes transferring the load more difficult. However, developing an optimal load transfer system makes meeting a certain volume target easier. The matrix makes it easy to identify this sort of relationship.

This is why identifying the relationships and the “also” questions are important. Where is your design focus? If the primary focus is on Cost Target, the focus is on an element that has little or nothing to do with the other elements. If it is on Increase Durability, it can be detrimental to elements like cost and weight.

When the design focus is on developing a good Transfer Load solution, meeting the volume target becomes easier, and so does durability. More importantly, when the focus is on answering the question, “How can we leverage the complementary elements of Transfer Load and Increase Durability to also benefit Lower Weight and Cost Target,” our energy and effort is focused on the most powerful elements of the design overcoming the most difficult.

We focus on using our most influential or powerful elements to overcome the most difficult. Can there be a better way to approach design? Use strength or good luck to overcome weakness or unfortunate circumstances.

I encourage readers to take a good look at the concept and make a concerted effort to put it to work. The matrix is merely a visual aid that captures what good problem solvers do intuitively. There are other tools and aids out there, in various formats that all try to make the same “also” opportunities apparent.

The key is not in the tool of choice, but in using the tool to identify the “also” opportunities. I used a product design example of a backpack. The concept and thought process works just as well for electronics, software, service solutions, business process improvement, and politics (in leadership and politics it’s called the “win-win” solution).

Take a good look at your design or problem-solving methods. Do your teams make a concerted effort to identify and leverage your opportunities?  It is the designs that do it all for less that are the remarkable ones. When we focus on the “also” questions we drive solutions that tend toward overcoming challenges that others do not or will not.

Don’t accept the conflicts and compromise around them. Instead, look for opportunities to leverage complementary elements to overcome conflicts. Spend your design energy on that and see what solutions can come of it.

Stay wise, friends.
