Positive and negative predictive values (PPVs and NPVs) are mentioned more and more, as they should be, given their clinical importance. Some (often?) times when PPV and NPV are discussed, the formula assumes that the prevalence is equal between the diseased and the normal populations. This does not take into account disease prevalence, which most often has dramatic results.… Read More ROC c-statistic (AUCs) Subtlety that is Often Forgot