Precision and Recall at One Half - Precision and Recall, Exactly

Compute both denominators at threshold one half.

highlighted = computed this step

Precision uses marked positives

Precision uses TP plus FP in the denominator: 2 + 1 = 3.

TP+FP=2 + 1=3

Precision is TP over TP plus FP, so it is 2 over 3.

\text{precision}={2\over3}

Recall uses TP plus FN in the denominator: 2 + 1 = 3, so recall is 2 over 3.

\text{recall}={2\over3}