# Area under the ROC curve accuracy [duplicate]

Why is the area under the ROC curve better than raw accuracy as an out-of- sample evaluation metric?

## marked as duplicate by gung - Reinstate Monica♦Aug 13 at 14:39

On the contrary the ROC curve plots the same concepts of 1-specificity ($$x_{i}$$) and sensitivity ($$y_{i}$$) for each given cutoff i on a $$(x_{i},y_{i})$$ coordinate system assuming that for each point in the plot the cutoff varies (so each point in the graph represents de facto the results in the contingency table obtained assuming that the cutoff is i). As you can see it can be considered a generalization of the contingency table approach for a generic i that is allowed to vary in the ROC plot. Therefore it allows to analyze the classification performance of the model (and the trade-off of specificity vs sensitivity) regardless the specific cutoff that you choose, thus segregating the two distinct important problems of choosing a good classification model per se (for any give cutoff), and then choosing a good cutoff. The AUC is just a numerical representation of the area under the ROC allowing to put the overall performance described by the ROC in a synthetic numerical form.