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A/B Test Significance Calculator
Drop in two variants and instantly know whether your winner is statistically real — or just random noise you would be unwise to ship.
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Variant A CVR
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Variant B CVR
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Relative Lift
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Confidence
Enter your numbers to see significance.
Confidence below 95% means the result could be random chance — do not ship it yet. This uses a two-tailed two-proportion z-test, the same standard real testing tools use.
Frequently asked questions
What is statistical significance in A/B testing?
It is the confidence that a difference between two variants is real and not random chance. 95% confidence is the standard threshold for calling a winner.
How large should an A/B test sample be?
Large enough to reach 95% confidence. Small samples produce noisy results that look like wins but disappear at scale.
What does relative lift mean?
Relative lift is the percentage improvement of variant B over variant A. A jump from 5% to 6% conversion is a 20% relative lift.
Run tests that actually compound.
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