Receiver operating characteristic (ROC) curves of four tests of association. For the definition of the four statistics, see the caption of Figure 4. Assuming 500 cases and 500 controls, a set of 20,000 sites were simulated under the null and under the alternative at individual sequencing depths of 2×, 5×, and 10× (three columns). At each false positive rate (x-axis), the corresponding critical value was computed using the empirical null distribution. The true positive rate (power; y-axis) was obtained by computing the fraction of causative sites with test statistics that exceed the critical value.