Heritability and genetic correlation: Statistical power, population comparisons, and sample size

Abstract

The question of statistical power as it relates to estimates of heritability and genetic correlation, particularly with reference to population comparisons, is briefly discussed. Power tables (α=0.05) are presented for estimates of heritability and genetic correlation for four research designs (the regression of offspring on mid-parent values, the regression of offspring on single-parent values, the intraclass correlation of full sibs; and the intraclass correlation of half sibs) as a function of sample size. In addition, tables of statistical power for the comparison of heritabilities obtained from two different populations, using these four methodologies, are presented. These tables indicate that, for the study of a single population, 400 families of four members each is a sufficient sample to achieve a statistical power in excess of 95% for a heritability estimate of 0.20. However, in the comparison of heritabilities from two populations, 800 families of four members each, measured in each population, would be required to achieve equivalent statistical power for a difference in heritability of 0.20.