General Discussions

F1 Score

F-score (F1score) is the harmonic mean of precision and recall.

Know About:
Harmonic Mean

Precision and Recall

We can write F score as:

F score = 2 * Precision * Recall / (Precision + Recall)


let us calculate for the example,  On a 1000 movie hard disk which had 200 thriller movies, all the movies which belonged to ‘thriller’ genre was separated out and 70 were listed out. Out of 70 that were separated, 40 were relevant. Find Precision and Recall.

A = number of relevant records retrieved = 40
B = number of relevant records not retrieved = 200 – 40 = 160
C = number of irrelevant records retrieved = 70 – 40 = 30

Precision = A / (A+C) = 40 / (40+30) = 40 / 70 = 0.5714 = 57.14%

Recall = A / (A + B) = 40 / (40+160) = 40/200 =  0.2 = 20%

F-Score = 2 * 0.5714 * 0.2 / (0.5714 + 0.2) = 0.2286 / 0.7714 = 0.2963

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