Validity and power analysis of union testing. Each simulated data set consisted of 938 cases and 863 controls. For each experiment, 1,000 independent replicates were simulated. Coded genotypes were simulated by randomly sampling from a binomial distribution with the given frequencies. Case-control status was determined by a logistic model. Gray lines indicate the per comparison significance threshold of 0.05. A) Per comparison error rate. Unions of one, two, three, four, and five SNPs are represented by black, red, orange, green, and blue lines, respectively. B) Power for an odds ratio of 1.5 for each SNP. C) Power for an odds ratio of 2 for each SNP. D) Power for 2-marker unions with opposing effects. The black line represents odds ratios of 2 and 0.5 for the two markers, the red line represents 1.5 and 0.67, and the blue line represents 1 and 1. E) Power for unions consisting of one predictor with an odds ratio of 2 (black line), 1.5 (red line), or 1 (blue line), and four predictors with odds ratios of 1. F) Power for 2-marker unions with correlated predictors. Solid lines represent independent predictors and dotted lines represent predictors correlated at r2 = 0.8. Black lines represent odds ratios of 2, red lines represent 1.5, and blue lines represent 1. G) Power to detect epistasis for 2-marker unions. The black line represents odds ratios of 1 for both markers and 1 for the epistatic effect. The red line represents odds ratios of 1 for both markers and 2 for the epistatic effect. The blue line represents odds ratios of 1 for both markers and 0.5 for the epistatic effect. H) Power to detect differential correlation between 2-marker unions. Black lines represent r2 = 0 in controls and r2 = 0.8 in cases. Red lines represent r2 = 0.8 in controls and r2 = 0 in cases. Solid lines represent odds ratios of 2 and dotted lines represent 1.