Variance (statistics)

In statistics, variance is a measure of how spread out data are around the mean.

Population variance is $\frac{Σ (x - μ)^{2}}{n}$ , and sample variance is $\frac{Σ (x - \bar{x})^{2}}{n - 1}$ . To use the same units as the data, we often use the standard deviation, the square root of the variance.