Yeast YPD pseudo-datasets: Type I error. Difference between actual and nominal Type I error rates vs. nominal Type I error rate, for different normalization procedures. The colored areas correspond to the most conservative and most anti-conservative curves obtained from the 35 YPD pseudo-datasets. The dashed line corresponds to a nominal unadjusted p-value of 0.05. The full-quantile GC-content normalization procedure yields the smallest area, meaning that the actual Type I error rate is closer to the nominal Type I error rate than with the other two procedures.