Inference, estimation, and decision-making from data
"Accuracy" sounds like the obvious way to score a classifier, right up until it lies to you. The right evaluation metric depends entirely on the task and the cost of different mistakes. Start with the confusion matrix: counts of true positives (TP), false positives (FP), true negatives (TN), and false negatives (FN). Every metric is built from these four numbers.
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▶ Evaluation Metrics