F1 Score
Domain: Evaluation
🎯 Motivation
The harmonic mean of precision and recall. A single number that balances both. Useful when you need one metric.
📋 Concrete Example
Precision = 0.8, Recall = 0.9. F1 = 2 * (0.8 * 0.9) / (0.8 + 0.9) = 0.847. One number that balances both metrics.
🔗 Analogy
A combined grade for two subjects - instead of separate math (85%) and English (90%) grades, an average (87.5%). F1 combines precision and recall into one score.