Cancer screening part 2: Validity - sensitivity and specificity

This video, the second in a section about cancer screening, describes measures of the validity of a screening test - sensitivity and specificity.

Validity measures are useful in telling us how good a test is, by describing how good they are at identifying people with the disease with a positive result, and those without it with a negative result.

Sensitivity is the probability that a test will correctly identify people who have the disease with a positive result. A test with a high sensitivity will ensure people with the disease aren’t missed by a test.

Specificity on the other hand, is the probability that the test will correctly identify people who don’t have the disease with a negative result. A test with high specificity will ensure we don’t have many people who don’t have the disease going on to have unnecessary further testing.