Calculate the power of a proportion test and the effect it can detect.
Power depends on sample size, baseline rate and the true effect. Comparing the observed lift with the minimum detectable effect shows immediately whether the test could ever have found it. A test whose minimum detectable effect exceeds any plausible business improvement is not worth running at all.
Statistical Power
Power derives from the z of the observed difference less the critical value
Power derives from the z of the observed difference less the critical value Power depends on sample size, baseline rate and the true effect. Comparing the observed lift with the minimum detectable effect shows immediately whether the test could ever have found it.
A test whose minimum detectable effect exceeds any plausible business improvement is not worth running at all.
This calculator takes 4 inputs: Sample size per group, Baseline rate, Observed rate in the variant, Significance level. The pre-filled defaults are a realistic starting point — replace them with figures from your own environment for a result you can act on.