The number needed to treat (NNT) is an epidemiological measure used in communicating the effectiveness of a health-care intervention, typically a treatment with medication.
The NNT is the average number of patients who need to be treated to prevent one additional bad outcome.
For example, if a drug has an NNT of 5, it means you have to treat 5 people with the drug to prevent one additional bad outcome (death, stroke, etc.).

See reference for more information.

Adapted from Wikipedia, the free encyclopedia. Internet. Accessed on December 15, 2018.