2.28 In comparing new and standard treatments with success probabilities and , the number needed to

2.28 In comparing new and standard treatments with success probabilities π₁ and π₂, the number needed to treat (NNT) is the number of patients that would need to be treated with the new treatment instead of the standard in order for one patient to benefit.

Explain why a natural estimate of this is 1/(π₁ – π₂).