Sensitivity measures how often a test correctly generates a positive result for people who have the condition that’s being tested for (also known as the “true positive” rate). A test that is highly sensitive will not generate many false-negative results and identify almost anybody who has the disease.
Specificity measures a test’s ability to correctly generate a negative result for people who don’t have the condition that’s being tested for (also known as the “true negative” rate). A test with a high-specificity will correctly rule out almost everyone who doesn’t have the disease and won’t generate many false-positive results.