False Positives and False Negatives

Tests can identify who has the novel Coronavirus (COVID-19). The Department of Health and Social Care updates the number of UK confirmed cases.

Confirmed cases must have a positive test result. Testing is imperfect. This article illustrates how false test outcomes affect our interpretations.


Imagine one in five people have a virus. We sample, and get a perfect slice of that population. Our sample of 100 people contains 20 patients with…