This article/section deals with mathematical concepts appropriate for late high school or early college. |

**Variance** is a measure in statistics of the dispersion of a set of values (represented as ). It is defined as

where the expected value of *X* is E(*X*).

The formula for variance must not be confused with the formula

which is the formula for a point estimate of the true variance from a sample of size *n*. As such this estimator itself has a variance which, as the formula indicates, decreases as the sample size increases.