Work out placebo response rate instantly with clear inputs, formula shown and shareable results.
The placebo response rate is often substantial - 32% here - and only the difference above it counts as drug effect. A 58% treatment response gives 26 percentage points of absolute benefit, a number needed to treat of 3.8. Reporting only the relative ratio of 1.81 obscures how much of the response placebo already delivered.
Absolute benefit
difference = treatment response rate - placebo response rate
Number needed to treat
NNT = 1 / absolute risk difference
Natural history, regression to the mean, expectation effects and the attention of trial participation all contribute. In depression trials placebo response often exceeds 30%.
Absolute difference and NNT, because relative measures can look impressive while representing a tiny absolute change.