# Variance

- The square of the difference from the mean for each data value, summed and divided by one less than the number of values. An expression of the so-called "second moment" which describes the variability around the mean. The square root of the variance is the standard deviation.

- for the data series:
*x*_{1},*x*_{2},*x*_{3},....,*x*_{N}the variance is:

**See also: **Mean, Standard Deviation, Standard Error, Statistic.

**Subjects: ** Statistics