A/B Test Significance
Run a two-proportion z-test on A/B test results. Enter visitors and conversions for each variant to see p-value, statistical significance, relative lift, and minimum sample size guidance.
A rate
5.000%
B rate
5.900%
Lift
+18.00%
z-score
1.982
p-value
0.0474
Significant?
Yes (p<0.05)
How to use the a/b test significance
Enter visitors and conversions for variants A (control) and B (treatment). The two-proportion z-test tells you whether the difference is statistically significant at p < 0.05.
Formula & explanation
z = (pB − pA) / √(p̂(1−p̂)(1/nA + 1/nB)) where p̂ is the pooled proportion. Two-sided p-value via the standard normal CDF.
Examples
A: 5000 visits, 250 conv (5.0%). B: 5000 visits, 295 conv (5.9%). Lift +18%, p ≈ 0.046 → significant.
Frequently asked questions
- What about small samples?
- z-test assumes large enough samples (typically np ≥ 5 in both arms). For very small n, use Fisher's exact test.
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