Figure 4
Power (at α = 5%) for the tri-allelic case for a representative scenario of two alleles ( A 2 and A 3 ) acting in opposite directions ( A 2 is protective, whereas A 3 is the susceptibility allele) with modest effect (OR = 0.77 for allele A 2 and OR = 1.3 for allele A 3 ) following distinct modes of action (A-B, dominant; C-D, multiplicative, E-F, recessive) under moderate heterogeneity (τ2 = 0.025). The sample size for each study was randomly sampled from a uniform distribution on the interval [500-1000] and split equally into cases and controls (i.e. case to control ratio = 1). Color lines depict power estimates under different models of analysis: orange (log-additive trend), blue (Dunn-Šidák-corrected per-allele odds ratio) and black (generalized odds ratio). Results are based on 5,000 replications under a random-effects model (DerSimonian-Laird method). f, allelic frequency. Scenarios with alternative magnitudes of heterogeneity or use of a fixed-effects model yielded qualitatively identical results.