Confidence intervals of sample means help measure the mean of a population. They’re easy to calculate with a spreadsheet. Let’s learn how to find confidence intervals in Microsoft Excel.
How to Find Confidence Intervals in Excel
For a mean, there are two confidence intervals: lower and upper. These form a range around your mean, and have a percentage likelihood. A 90% interval, for example, suggests that 90 of 100 intervals sampled will contain the mean value.
Consider a dataset where you need to find the confidence interval. To begin, navigate to the Data tab on Excel’s ribbon. On the far right side, click on the Data Analysis button. You’ll see the Data Analysis popup menu, which contains a long list of Analysis Tools.
To find the confidence intervals, you’ll want to select Descriptive Statistics. Choose this option from the list, then click OK.
You’re now on the Descriptive Statistics menu. Here, you’re given a few choices for your data. First, click into the Input Range box. Then, click and drag to highlight the relevant data on your spreadsheet. In this case, that’s cells A2:A6.
Since this data is in a column, leave the Columns button selected. To include your labels, click Labels to incorporate the headers. Check the Summary Statistics box.
Finally, Confidence Level for Mean asks you to specify your desired confidence interval. It defaults to 95%, which is commonly used in statistics.
When you’re finished, click OK. You’ll see a data report on a new worksheet. At the bottom is your confidence interval. To find your upper confidence interval, add cell B16 to cell B3 (your mean). To find the lower confidence interval, subtract cell B16 from cell B3.
As you can see, Excel takes the hard work out of finding confidence intervals for sample data. This is a useful statistical analysis that you can perform over and over again.
Coefficient of Variation