Statistics & Probability
Intermediate

Sample Variance

Unbiased estimate of population variance.

Formula

s2=1n−1∑(xi−xˉ)2s^2 = \frac{1}{n-1}\sum(x_i-\bar{x})^2

Variables

x_iValues
\bar{x}Mean
nSize

Example

Uses n-1 (Bessel correction)

Did You Know?

Sample variance divides by n−1, not n — Bessel's correction that stops it from systematically underestimating spread.

spread