It’s easiest to think of them as true positive rate and true negative rate, respectively.
For example, when considering the chance of getting cancer (C or notC) and the result of a cancer test (Pos or Neg).
- Sensitivity is the probability of getting cancer given the test result is positive – Pr(C | Pos);
- Specificity is the probability of not getting cancer given the test result is negative – Pr(notC | Neg).