# What is the variance of {17, 3, 10, 1, -3, 4, 19}?

##### 1 Answer

Population variance = 59.1 (probably what you want if this is an introductory class)

Sample variance = 68.9

#### Explanation:

Calculate the mean

Find the mean of the squared differences. To do this:

Square the difference between each data point and the mean. Add all of these squared differences.

If you're finding the population variance*, divide by number of data points. If you're finding the sample variance*, divide by the number of data points - 1.

Round in whatever way you've been told to.

**If these are all the data points in the set, i.e. represent the entire population of data points, use the population variance.*

*If these data points are a sample of the data, i.e. there is a lot of data you're missing, but you want an accurate calculation for all of the data, use sample variance.*

This WikiHow page has a detailed explanation for how to calculate the population and sample variance, with examples of when each would be appropriate.