Free Rowform tool

Free Statistical Significance Calculator

Compare two conversion rates with a two-sided, pooled-proportion z-test for an A/B experiment.

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How to Use This Statistical Significance Calculator

Enter visitors and conversions for control A.
Enter visitors and conversions for variation B.
Choose a confidence threshold and review the two-sided test result.

What is statistical significance?

Statistical significance estimates whether an observed A/B difference is unlikely under a no-difference assumption. It does not measure business value, remove bias, or replace a pre-planned sample size.

The Formula

Z = (p₂ - p₁) ÷ √[p(1-p)(1/n₁ + 1/n₂)]

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Frequently Asked Questions

Is this a one-sided or two-sided test?

It is a two-sided test, so it detects a difference in either direction.

Should I stop as soon as the result is significant?

Repeatedly checking and stopping early can inflate false positives. Set a sample size and test duration before starting whenever possible.