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.
