Sensitivity and Specificity
Etymology
“Sensitivity” is from Latin “sensus” (feeling, perception); “specificity” from “species” (kind, sort), via “specific.” The pair was introduced to diagnostic testing by Jacob Yerushalmy in 1947 to evaluate screening reliability.
noun phrase · /sen-sih-TIV-ih-tee and spes-ih-FIS-ih-tee/
The two ways of scoring a test: how many real cases it catches, and how many non-cases it correctly clears.
What it names
It puts the two failure modes of any test on the table at once, so “accurate” stops being a single vague word.
Example
A highly sensitive test rarely misses true cases but may over-flag; a highly specific one rarely false-alarms but may let cases slip through.
Related idea
Sensitivity is about avoiding false negatives and specificity about avoiding false positives; a test can be superb on one and poor on the other, which is why a single “percent accurate” figure is nearly useless.