# Precision/Recall/Accuracy

•                 |   Positive (Actual)  | Negative (Actual)


———————–|———————-|———————– Positive (Prediction) | True Positive (TP) | False Positive (FP)
Negative (Prediction) | False Negative (FN) | True Negative (TN)

• Precision (適合率、精度): Of examples recognized as positive, what percentages are actually positive? $${\rm Precision} = \frac{\rm TP}{{\rm TP} + {\rm FP}}$$

• Recall (再現率): What percentages of actual positives are correctly recognized as positive? $${\rm Recall} = \frac{\rm TP}{{\rm TP} + {\rm FN}}$$

• Accuracy (正解率): $${\rm Accuracy} = \frac{\rm TP}{{\rm TP} + {\rm TN}}$$