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A/B test significance — free calculator
Two-tailed z-test for comparing conversion rates between two variants. See uplift, confidence and whether your winner is real.
Variant A (Control)
Variant B
Results
Confidence97.17%
VerdictVariant B wins
Conversion rate A5.00%
Conversion rate B6.00%
Relative uplift20.00%
p-value0.0283
95% confidence is the standard threshold to call a winner.
Guide
How A/B test significance works
This calculator runs a two-tailed z-test on pooled proportions. It answers: "given these numbers, what's the probability the difference is due to chance?" A p-value below 0.05 (95% confidence) usually means you have a real winner.
Do this before you call the test
- • Decide your sample size in advance — don't peek early.
- • Run for full business cycles (typically at least 1–2 weeks).
- • Split traffic randomly, not by user attribute.
- • Only test one change per experiment to attribute the lift.
Run experiments on your live traffic
Thrivio Journeys audits how visitors move through your funnel — pinpointing where to test next.
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