# Variance

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:

$1$ .  Find the mean of the scores $\left(\stackrel{¯}{x}\right)$ .

$2$ .  Subtract the mean from each individual score $\left(x-\stackrel{¯}{x}\right)$ .

$3$ .  Square each of the differences obtained above.  ${\left(x-\stackrel{¯}{x}\right)}^{2}$ .

$4$ .  Add all of the squares obtained in step $3$ . $\left(\sum {\left(x-\stackrel{¯}{x}\right)}^{2}\right)$ .

$5$ .  Divide the total from step $4$ by the number $\left(n-1\right)$ , where $n$ is the total number of scores used.