Guide for Determining the Confidence Interval Using Excel

1. Click in another empty cell.

2. Click the Function icon.

3. Scroll and choose Confidence. Click "OK."

The following dialogue box will appear.

4. In the box labeled Alpha, insert the Alpha level you wish to use in your analysis (For example, .05 for a 95% confidence interval).

5. Click in the box labeled Standard_dev and type in the value computed in the STDEV function performed above.

6. In the box labeled Size, insert the number of data points in the sample.

7. Click OK, and the confidence interval will be computed.

8. Add and subtract the confidence interval value from the mean found above to find the confidence interval range.

Original work on this document was done by Central Virginia Governor's School students Jennifer Rice, Eliza Evans, and Chris Earle (Class of '03).

Copyright 2002 Central Virginia Governor's School for Science and Technology, Lynchburg, VA