#### Using Standard Deviation

The *mean* can be used to describe the typical or common value in a data set.

The *standard deviation* describes a data set by giving the average of the distances from the mean. The greater the range of the data, the greater the standard deviation.

## Example

The average (arithmetic mean) supermarket checkout wait time is 4 minutes with a standard deviation of 1 minute 37 seconds (1.6 minutes).

(a) The average wait time in Atlanta, Georgia is 1 standard deviation below the mean. What is the average wait time in Atlanta?

(b) The average wait time in Washington, D.C. is 8 minutes 23 seconds (8.38 minutes). How many standard deviations is Washington’s wait time from the mean?