Figure 1
From: Trick or treat: The effect of placebo on the power of pharmacogenetic association studies
(a) The effect of genotype relative risk (GRR) ratio and placebo effect ( f 0 ) on the power of detecting an association between the causative single nucleotide polymorphism (SNP) and the response to the drug. Power estimates are plotted against the number of persons per trial for different values of f2 (penetrance among homozygotes for the response allele), f0 and GRR values. GPC refers to the Genetic Power Calculator program, which does not take into account the placebo effect. The horizontal broken line denotes the 80 per cent power threshold. (b) The relative effect of f2 and f0 on the power of detecting an association between the causative SNP and the response to the drug. The number of persons per trial equals 1,000. Results are based on 1,000 simulations.