Free A/B-test calculator by @onlinedialogue for

Test result

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Variation B's observed conversion rate () was higher than variation A's conversion rate (). You can be 95% confident that this result is a consequence of the changes you made and not a result of random chance.
The observed difference in conversion rate () isn't big enough to declare a significant winner. There is no real difference in performance between A and B or you need to collect more data.

The expected distributions of variation A and B.

Conversion Rate Control
Conversions A / Visitors A

Conversion Rate B
Conversions B / Visitors B

Relative uplift in Conversion Rate


Observed Power

p value

( CRB - CRA ) / SEdifference

Standard error A
( CRA * (1-CRA ) / VisitorsA)1/2

Standard error B
( CRB * (1-CRB ) / VisitorsB)1/2

Std. Error of difference
SEdifference = ( SEA2 + SEB2 )1/2