Current Incentives for Scientists Lead to Underpowered Studies with Erroneous Conclusions
The figure shows the proportion of published studies that are correct 1 − PT (A, B), the total number of published studies NC + NC (C, D), and the total scientific value of research VS (E, F). We varied the following parameters: the probability of a Type I error α (A, C, E), and the dependence of acceptance on sample size m (B, D, F). The lines show predictions for two values of the probability that an effect is real (fE) and two values of the effect size (solid: fE = 0.2, rC = rE = 0.21; dotted: fE = 0.3, rC = rE = 0.21; dashed: fE = 0.2, rC = rE = 0.32). Other values: NC = 120, T = 2,000, k = 20, α = 0.05, σ2 = 1, m = 3, ϕ = 0.55, and γ = 0.055.