Distribution example. Example two-gene distributions with multivariate effects. Each square/cross denotes a sample from one of the classes. Black dashed/gray solid lines denote the corresponding class-conditional marginal distributions. A: A PCWT distribution where the gene X2 is UDE (since its class-conditional means differ) while X1 is not. B: A PCWT distribution where neither gene is UDE (and hence cannot be detected by standard differential expression tests). C: A non-PCWT distribution. In all cases, both genes are MDE.