View source for Inbreeding (population sense)

An assumption of Hardy–Weinberg genotype proportions is alleles are paired independently of each other. This can be referred to as random mating in a popualtion. 

<math>F_{IS} = \frac{H_S - H_I}{H_S}</math>

where

<math>H_I</math> is the observed frequency of heterozygous genotypes in a popualtion. (<math>I</math> refers to Individual.)

<math>H_S = 2 p (1 - p) </math> is the expected frequency of heterozygous genotypes in a popualtion. In this example it is given for the case where there are only two alleles. (<math>S</math> refers to Subpopulation.)

<math>F_{IS}</math> can be incorporated into expectations of genotype frequencies by adjusting Hardy–Weinberg proportions.