When computing the F1 score for an imbalanced binary classification problem, which formula is correct?
Select an answer to reveal the explanation.
Short Explanation and Infographic
Here's the deal — d is correct because both formulas B and C are mathematically equivalent expressions of the F1 score. Formula B (harmonic mean of precision and recall) is the standard presentation.
Full explanation below image
Full Explanation
D is correct because both formulas B and C are mathematically equivalent expressions of the F1 score. Formula B (harmonic mean of precision and recall) is the standard presentation. Formula C substitutes the definitions of precision and recall into B and simplifies to TP / (TP + 0.5*(FP+FN)), which is identical. A is wrong because it computes the arithmetic mean, not the harmonic mean.