1. Section 12.4
Standard Deviation

2. Finding Standard Deviation
Definition 1: Statisticians use several measures of variation to describe how the data in a data set are spread out.
Definition 2: The range of a set of data is the difference between the greatest and least values.
Definition 3: The interquartile range is the difference between the third and first quartiles.

3. Example 1
Thirteen men qualified for the 2002 U.S. Men’s Alpine Ski Team. Find the range and the interquartile range of their ages at the time of qualification:
27, 28 29, 23, 25, 26, 26, 28, 22, 23, 23, 21, 25

4. Finding Standard Deviation
Definition 4: Another measure of variation is the standard deviation, a measure of how much the values in a data set vary, or deviate, from the mean. The Greek letter σ (sigma) represents standard deviation.

5. Example 2 Find the mean and the standard deviation for the values:
48.0, 53.2, 52.3, 46.6, 49.9

6. Example 3
Energy Find the mean and standard deviation of the data for daily energy demand in a small town during August.

7. TOTD
There are 9 members of the Community Youth Leadership Board. Find the range, interquartile range, and standard deviation of their ages: 22, 16, 24, 17, 16, 25, 20, 19, 26.