Precision and Recall
Domain: Evaluation
🎯 Motivation
Precision: of the positive predictions, how many are correct? Recall: of the actual positives, how many did we find? Both matter.
📋 Concrete Example
Medical test: precision = of patients diagnosed, how many actually sick? Recall = of sick patients, how many did we catch? High precision = few false alarms. High recall = few misses.
🔗 Analogy
Fishing with a net: precision = of what you caught, how many are target fish (not junk)? Recall = of all target fish in the sea, how many did your net catch? Both matter.