# Statistics Guide: A study of long-distance phone calls made from General Electric Corporate Headquarters

In this tutorial, we provide an image of the formatting in an excel spreadsheet. For each problem we show the actual formula to plug into the cell and the result.

Student Question: A study of long-distance phone calls made from General Electric Corporate Headquarters in Fairfield, Connecticut, revealed the length of the calls, in minutes, follows the normal probability distribution. The mean length of time per call was 4.70 minutes and the standard deviation was 0.50 minutes.

### What fraction of the calls last between 4.70 and 5.50 minutes?

=NORM.DIST(5.5,C7,C8,TRUE)-0.5

Result: 0.4452

### What fraction of the calls last more than 5.50 minutes?

=1-NORM.DIST(5.5,C7,C8,TRUE)

Result: 0.0548

### What fraction of the calls last between 5.50 and 6.00 minutes?

=NORM.DIST(6,C7,C8,TRUE)-NORM.DIST(5.5,C7,C8,TRUE)

Result: 0.0501

### What fraction of the calls last between 4.00 and 6.00 minutes?

=NORM.DIST(6,C7,C8,TRUE)-NORM.DIST(4,C7,C8,TRUE)

Result: 0.9146

• Student: Brandy Golden