The variance (this term was first used by Fisher, 1918a) of a population of values is computed as:

s2 = S(xi-m)2/N

where

m |
is the population mean |

N |
is the population size |

The unbiased sample estimate of the population variance is computed as:

s2 = S(xi-xbar)2/n-1

where

xbar |
is the sample mean |

n |
is the sample size. |

See also, Descriptive Statistics.