1. 10.2 Variance
Math Models

2. Types of dispersion:
In statistics, measures of dispersion describe how spread apart the data is from the measure of center. There are three main types of dispersion:
Range - the difference between the highest and lowest values in the data.
Variance - the mean of the squares of the distance each data item (xi) is from the mean. The symbol for variance is
Standard deviation - the square root of the variance.

3. Find the variance for the following data: 11, 13, 14, 15, 19, 22, 24, 26.
First find the mean

4. It’s easier to create a table of the differences and their squares.

5. Compute the variance:
The variance is a measure of the dispersion and its value is lower for tightly grouped data than for widely spread data. In the example above, the variance is 27.

6. Standard deviation measures how closely the data clusters around the mean. It is the square root of the variance. Its symbol is