We simulated realistic baseline enrichment plus enrichment in a cell-type group (see Online Methods), and we performed our cell-type group analysis on the resulting summary statistics. First, we calibrated simulated enrichment of the causal cell-type group to give us a realistic average top −log10(P) based on results for the real data sets analyzed below (Online Methods). Of the simulations in which at least one cell-type group reached significance, we found that the top cell-type group was the cell-type group simulated to be causal 99% of the time (Figure 3). Next, we simulated weaker enrichment, calibrated so that only 50% of replicates included a significant cell-type group. In these simulations, the cell-type group simulated to be causal was the top cell-type group in 95% of simulations with at least one significant cell-type group, and a cell-type group with r2 > 0.5 to the causal group was the top cell-type group in half of the remaining simulations with at least one significant cell type (Figure 3). Results separated into the ten individual cell-type groups are displayed in Supplementary Figure 5.
