In a genetic association study, as the sample size grows, the effect of population substructure becomes more serious. If not modeled correctly, even subtle correlations between individuals of common ancestry begin to affect the distribution of tests of association causing a greater number of spurious associations [7-9]. Thus, for sound inferences from GWAs, especially those using samples of diverse ancestry, it is important to control for ancestry differentiation. Family-based samples and association analyses, such as trios of parent and affected offspring and analyzed by FBAT [37], are robust to population structure.
