Question

In the "Input Analysis" section of the spreadsheet model, calculate the 95% confidence interval for the sales for each type of product. (You will not calculate a confidence interval for attendance.) Use the number of events (calculated in cell I3) as part of your calculations. (Note to Excel 2007 users: the CONFIDENCE.NORM function is not supported in Excel 2007. Use the CONFIDENCE function instead.) [5 points]

Answer 1

The Formula to use is given as

`=CONFIDENCE.NORM(0.05,J3,I3)` for excel 2010 and above and

`=CONFIDENCE(0.05,J3,I3)` for excel 2007 and below.

Explanation:

The formula to calculate the confidence interval is given as below

`=CONFIDENCE(ALPHA,STD DEV, SIZE)`

Here

• ALPHA is the value calculated as below

`\alpha=1-(confidence\, interval\%)/(100)`

• Value of ALPHA in this case is 0.05.

• STD DEV is the standard deviation, which is this case is supposedly in cell J3.

• SIZE is number of events which in this case is in cell I3.

So the formula to enter in the cell is

`=CONFIDENCE.NORM(0.05,J3,I3)`