Culverhouse et al. [2013] found that when all individuals receive the same weights in the PCA analysis, the top three PCs separate members of three of the largest pedigrees from the other samples. For the PCA based on proportional weighting of families, the top two PCs separated four families from the rest of the sample, where one of pedigrees was also identified as an outlier in the unweighted PCA, and the three smallest pedigrees in GAW18 were the other outliers.
