For population-based genetic association studies, such as case-control studies, the confounding effect of genetic ancestry can be controlled for by regressing out the eigenvectors [Price et al., 2006], matching individuals with similar genetic ancestry [Luca et al., 2008; Rosenbaum, 1995], or clustering groups of individuals with similar ancestry and using the Cochran-Mantel-Haenszel test. In each situation, spurious associations are controlled better if the ancestry is successfully modeled, but power is reduced if extra dimensions of ancestry are included.
