We calculated the weighted average of each of the four (co)variance components over the three cohorts by their sample size, i.e. Σi (Vg(i) ni)/Σi (ni) with the subscript i indicating the cohort and n being the sample size. From the results of these partitioning analyses within families we can infer what the prediction R2 (Equation 19 in Online Methods below) and what the proportion of variance explained by SNPs (i.e. Vg/VP with VP being the phenotypic variance) would be in a sample of unrelated individuals when using the same set of SNPs. We then tested these inferred values in unrelated samples.
