The effective sample size was somewhere between the number of independent families (2299), and the number of individuals (7181). For single variant tests on the primary traits, this resulted in 80% power to identify a SNP effect with r2 between .005 and .015 assuming alpha=3.4×10−7, the Bonferroni correction for all variants with MAF<.05. While power appears reasonable, it is important to note that for a very rare single variant, such as one with MAF=.1%, an r2 of .005 corresponds to a 0.5 standard deviation increase in the trait for each rare allele an individual possesses, a very large effect. Power for burden tests depends on, among other things, assumptions about direction of effect, the number of SNPs within a region, and the proportion of causal SNPs. We therefore refer the reader to prior publications on VTCMC and SKAT(38, 39).
