NNT (number needed to treat)

The NNT is 1 divided by the risk difference: among that many people in the compared group rather than in the other, one event more or less occurs. NNTB stands for one additional benefit, NNTH for one additional harm.

Example: NNTB 110.3 (95% CI NNTB 79.8 to 176.7). If the risk difference includes 0, the interval reads: NNTH 20.0 to ∞ to NNTB 4.0.

Caution: The interval of the NNT runs through infinity when the risk difference can also be 0 - never read it as an interval with negative numbers. Whether an event is desirable has to be stated by the person.