In most data mining applications, accurate ranking and probability estimation are essential. However, many traditional classifiers aim at a high classification accuracy (or low error rate) only, even though they also produce probability estimates. Does high predictive accuracy imply a better ranking and probability estimation? Is there any better evaluation method for those classifiers than the classification accuracy, for the purpose of data mining applications? The answer is the area under the ROC (Receiver Operating Characteristics) curve, or simply AUC. We show that AUC provides a more discriminating evaluation for the ranking and probability estimation than the accuracy does. Further, we show that classifiers constructed to maximise the AUC score produce not only higher AUC values, but also higher classification accuracies. Our results are based on experimental comparison between error-based and AUC-based learning algorithms for TAN (Tree-Augmented Naive Bayes).
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