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Minimum Detectable Effect Calculator

Calculate the minimum lift detectable in an A/B test given your sample size, set test expectations.

CRO
Minimum detectable lift
22.5% relative
Absolute: 0.68% (pp)
With more traffic, MDE shrinks
∝ 1/√n
4x sample size = ½ MDE
Don't declare results on tests where actual lift < MDE — your test couldn't have reliably detected such a small change.

About this tool

MDE tells you the smallest lift your test can reliably detect. Calculator handles baseline CR, sample size, alpha, power.

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