Definition
Plain language
A single score that balances how often you find what's there against how often you raise false alarms.
As stated in the literature
The harmonic mean of precision and recall, used as a single-number summary of classification quality.
Also called: F1 score
Why it matters: It captures the tension between missing things and crying wolf in one number, which makes it the default summary metric for classification tasks.
For example, a spam filter that catches 90% of spam but flags lots of real mail as spam will have a lower F1 than one that catches 80% but rarely misfires.
Heard on the show
“On discovery — just finding the bugs, not exploiting them — slyp hits an F1 score of zero point nine seven three.”Episode 024 — An AI Agent That Found 28 Zero-Days in Windows — And What Made It Work