= Number needed to treat
{title2=$\mathrm{NNT}=1/(p_C-p_I)$}
{wiki}
For a beneficial intervention reducing an adverse-event risk from $p_C$ to $p_I$ over a stated follow-up period, the <number needed to treat> is the reciprocal of the absolute risk reduction. Its clinical interpretation requires the population, outcome, horizon and comparison to be specified. Invert confidence limits for the risk difference in reversed order if both are positive. If the interval includes zero, the transformed confidence set is unbounded and may include both benefit and harm, rather than being one ordinary finite interval.
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