The above advantage is also clear when we consider that power in the separate AA sample is impacted by allele frequency differences. For a "true" locus having the allele frequency pattern of rs16969968, a large AA sample would be needed to ensure a significant result in EAs and also in AAs separately, because of the low MAF in AAs. For example, using standard power calculations for an allelic test [19], assuming the observed allele frequencies of 33% in EAs and 5% in AAs, prevalence of 3%, and a genotypic odds ratio of 1.4, our sample sizes attain 75% power at an alpha of 0.05 in the EAs, compared to only 27% power in the AAs. Nevertheless, our available sample sizes still allow useful filtering of the correlated set.
