Tool 08 · Calculators

A/B Test Significance

Know when an ad or page test is real signal, not noise — two-proportion z-test at 95% confidence, recomputed live.

Variant A (Control)

Visitors

Conversions

Conversion rate: 3.00%

Visitors

Conversions

Conversion rate: 4.20%

Significant — winner is B

Conversion Rate A

3.00%

control

Conversion Rate B

4.20%

challenger

Absolute Lift

1.20pp

B − A

Relative Lift

+40.0%

lift vs A

Z-Score

2.04

test statistic

P-Value

0.0416

two-tailed

Significant — winner is B. You can stop the test and ship the winner.

Estimated visitors per variant to reach significance for the current effect size (80% power, 95% confidence).

Target / Variant

3,856

More for A

1,856

More for B

1,856