(1) Precision

Precision indicates the proportion of the sample whose real category is positive in the sample with a positive prediction category. The calculation formula is shown below.

$$P = \frac{TP}{TP + FP} \tag{32}$$

(2) Recall Rate

The recall rate indicates that the proportion of the sample with a positive prediction category in the sample with a real positive category. The calculation formula is shown below.

$$R = \frac{TP}{TP + FN} \tag{33}$$

where the precision *P* and the recall rate *R* are a pair of contradictory indicators. In general, when the precision is high, the recall rate tends to be low. When the recall rate is high, the precision tends to be low.

#### (3) *F*1 Score

The *F*1 score takes the precision and recall rate into account and is their weighted harmonic mean. When the weights of precision and recall rate are the same, the harmonic mean obtained is called the *F*1 score, and the calculation formula is shown below.

$$F1score = 2 \times \frac{P \times R}{P + R} \tag{34}$$
