Average statistical power of simulated case-control scores in African Americans computed using (a) typed or (b) imputed genotypes.

For each score we list the proportion of SNPs for which the score attains genome-wide significance (defined as P<5e-08 for all scores except ADM, P<1e-05 for ADM), for random SNPs as well as SNPs in the top decile of population differences (Δ>0.4), for R = 1.2, R = 1.5, R = 2.0 simulations (see main text). For R = 1.0 the power is 0 for all scores. In general the MIX score shows an increase in statistical power relative to the ATT score, and a further increase in power relative to the SNP1 score, which is analogous to disease mapping in European or African populations. ATT-dose denotes ATT test using imputation dosages.