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A/B Test Calculator
Calculate statistical significance for A/B tests with Z-test, Chi-squared, Bayesian posterior analysis, power curves, and sequential testing simulation.
Control (A)
Rate: 5.00%
Variant (B)
Rate: 7.50%
Statistically Significantat 95% confidence
p-value (Z-test)
0.0000
Z-statistic
5.164
Relative uplift
+50.00%
Chi-squared
26.667
Chi-squared p-value
0.0000
Effect size (Cohen's h)
0.1038
CI width
1.895pp
Min. detectable effect
0.948pp
Sampling Distributions
Confidence Interval (B - A)
1.552% to 3.448% — interval excludes zero, difference is significant
All computations run entirely in your browser. No data is sent to any server. Math implemented from scratch using error function approximation (Abramowitz & Stegun) and Lanczos gamma approximation.