Читать книгу Medical Statistics - David Machin - Страница 84

A further summary measure, sometimes used in clinical trials is the number needed to treat. This is defined as the inverse of the ARD.

This is the additional number of people you would need to give a new treatment to in order to cure one extra person compared to the old treatment. Alternatively, for a harmful exposure, the number needed to treat becomes the number needed to harm and it is the additional number of individuals who need to be exposed to the risk in order to have one extra person develop the disease, compared to the unexposed group. The NNT is a number between 1 and ∞; a lower number indicates a more effective treatment. When there is no difference in outcome between the test and control groups, that is, ARD = 0, then the NNT is 1/0 which is infinity ∞.