The first step is gather the data you want to base the confidence calculation into an excel spread sheet. Put them all in a column and use the COUNT function to determine the number of data points you want to base you calculation on.In this case, there are 20 data points and the value of the count calculation is 20. Calculate the standard deviation of the data.The standard deviation is used to measure the variability of a data set and it is a key value of the confidence calculation. In Excel, this is done with the STDEV function.
S is the standard deviation of the sample and n is the sample size. Now I would like to show how Excel is used to develop a certain confidence interval of a population mean based on this small sample information. As you see, to evaluate this formula you need the mean of the sample and the margin of error. In this formula is the mean of the sample. is the interval coefficient providing an area of a/2 in the upper tail of a t distribution with n-1 degrees of freedom which can be found from a t distribution table (for example the interval coefficient for a 90% confidence level is 1.833 if the sample is 10). Sample size. Formula. Description. Result. =CONFIDENCE(A2,A3,A4). Confidence interval for a population mean. In other words, the confidence interval for the underlying population mean for travel to work equals 30 ± 0.692952 minutes, or 29.3 to 30.7 minutes. Now, like the calculation of the confidence interval for the large sample, calculate the confidence interval of the population based on this small sample information. The confidence interval is: We can be 90% confident that the true mean of the population, based on sample information, is between $6.39 and $7.21. In this formula is the mean of the sample. is the interval coefficient providing an area of a/2 in the upper tail of a t distribution with n-1 degrees of freedom which can be found from a t distribution table (for example the interval coefficient for a 90% confidence level is 1.833 if the sample is 10). The first step is gather the data you want to base the confidence calculation into an excel spread sheet. Put them all in a column and use the COUNT function to determine the number of data points you want to base you calculation on. In this case, there are 20 data points and the value of the count calculation is 20. Calculate the standard deviation of the data. The standard deviation is used to measure the variability of a data set and it is a key value of the confidence calculation. In Excel, this is done with the STDEV function.  5. Calculate your margin of error. You can find the margin of error by using the following formula: Za/2 * σ/√(n). Z a/2 = the confidence coefficient, where a = confidence level, σ = standard deviation, and n = sample size. This is another way of saying that you should multiply the critical value by the standard error.  Microsoft Excel, a spreadsheet computer program, offers a formula called CONFIDENCE to calculate the confidence interval. The interval represents the range from the survey value in which the true proportion is likely to exist. Enter the standard deviation in cell A2. For example, if your standard deviation equals 1.1, enter 1.1 in cell A2. Enter the sample size in cell A3. For example, if your sample size equals 3,000, enter 3,000 in cell A3. Enter CONFIDENCE(A1,A2,A3) in cell A4 and Excel will display the confidence interval. In this example, Excel will display 0.041245769 meaning your confidence interval equals plus or minus 4.12 percen A 99% Confidence interval for a parameter of the population (say, the mean) means that in 99% of the cases (99% of the samples, if you were to repeat the sampling process many times) the true parameter (in our case, the mean) will fall inside this interval.  Confidence Function Example. In the spreadsheet below, the Excel Confidence Function is used to calculate the confidence interval with a significance of 0.05 (ie. a confidence level of 95%), for the mean of a sample of heights of 100 men. The sample mean is 1.8 meters and the standard deviation is 0.07 meters. The Excel CONFIDENCE function uses a Normal Distribution to calculate a confidence value that can be used to construct the Confidence Interval for a population mean, for a supplied probablity and sample size. It is assumed that the standard deviation of the population is known. The format of the function is:
http://dmcslab.netlab.uky.edu/~qjian2/links/stat/ci/stat_confide.html https://support.office.com/en-us/article/CONFIDENCE-function-75CCC007-F77C-4343-BC14-673642091AD6 http://dmcslab.netlab.uky.edu/~qjian2/links/stat/ci/stat_confide.html http://www.infobarrel.com/How_to_calculate_95_confidence_intervals_using_Excel http://www.wikihow.com/Calculate-Confidence-Interval http://www.ehow.com/how_8240838_use-excel-calculate-confidence-interval.html http://users.business.uconn.edu/jstallaert/opim5103pm/anc/Confidence%20Intervals.pdf http://www.excelfunctions.net/Excel-Confidence-Function.html
how to determine confidence interval in excel