Fig. 1  The statistical power for the allelic test in a case-control study according to (A) minor allele frequency (MAF), (B) disease prevalence, (C) linkage disequilibrium (LD), and (D) case-to-control ratio (M, MAF; P, prevalence; D, LD; R, case-control ratio; A1=1.3, A2=1.5, A3=2, and A4=2.5 for heterozygous odds ratios).