Most initial GWAS samples included 500-3,000 cases (plus controls), or as high as 10,657 subjects for a continuous trait. One or more replication samples were usually then studied via collaboration, totaling 2,000-8,000 subjects (cases and controls, or family members). For studies with at least 1,000 cases, most findings involved common alleles (20-80%) with odds ratios (ORs, estimates of GRR) between 1.1-1.4, i.e., the range within which there was some power.
