Variance is the measure of statistical dispersion, that is, the variation among the different samples in a data set. It is the average of the squared differences from the mean .
Variance is the square of the standard deviation . If you do not know the standard deviation, you can use the following procedure to determine the variance.
Procedure for Finding the Variance:
. Find the mean of the scores .
. Subtract the mean from each individual score .
. Square each of the differences obtained above. .
. Add all of the squares obtained in step . .
. Divide the total from step by the number , where is the total number of scores used.