One-vs-Rest (OvR) AUROC
Each OvR AUROC compares one class with its own negative mixture. Interpret the mixture and finite-sample variation before comparing class scores.
Each OvR AUROC compares one class with its own negative mixture. Interpret the mixture and finite-sample variation before comparing class scores.
The same credit scores gave a credit-risk Gini of 0.6706 and an economics Gini of 0.4601. The analogy between the two curves is not an identity.
AUROC and Gini preferred one model, KS and average precision preferred the other. All four are described as measures of discriminatory power.
In single-label problems the pooled positive rate is 1/K, providing a no-skill reference for micro average precision rather than a guaranteed floor.
Three classes with similar ROC-AUC score 0.96, 0.59 and 0.23 on average precision. Prevalence changes how these metrics should be read.
The ranking view and the area view give the same value. Where the term is ambiguous, how ties are counted, and what AP is not.
Two models with the same area can differ 2.5-fold in what they catch at a workable false positive rate. What to report beside the number.