Figure 1.

Type I errors in the absence of differential expression variability. There are n samples of cases and controls each and varying proportions of excess zeros s. The MDSeq, Levene's tests, and heteroscedastic regression have well controlled type I errors for moderate to large sample sizes, whereas Bartlett's and MAD tests have highly inflated type I errors. Results are based on 1,000 simulations without additional covariates. Reference lines (in red) are drawn at the 0.05 error rate.