To calculate simple variance, also called sample variance, start by calculating the mean of the set of numbers. Next, subtract the mean and square the result for each number. Finally, add the squared results, and divide this sum by one less than the number of data points.
- Calculate the mean
Perform a simple average of all the numbers in the set.
- Subtract the mean and square the result
Subtract the mean from each number in the set and square each result.
- Add the results
Calculate the sum of all of the squared results from the previous step.
- Divide the sum by one less than the number of data points
Divide the sum from the previous step by one less than the number of data points in the original set. The resulting number is considered sample variance and is closely related to sample standard deviation, which is found by taking the square root of this final number.