A/B Test Calculator

Jeff Sauro, PhD

Compare two independent proportions for A/B testing or comparing completion rates or conversion rates for small and large sample sizes.

Group 1
Group 2

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About this calculator

This calculator is based on the N-1 Chi-Square test as orginally proposed by Pearson, 1900 and recommended by Campbell, 2007. When expected cell counts fall below 1, the Fisher Exact test is used. Detailed calculations and examples are available in Chapter 5 of Quantifying the User Experience.

In general you should use the 2-tailed p-value unless you have a strong a priori reason to suspect one group really will have a higher proportion.

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