Calculating Statistical Significance for Your A/B Tests
 

An A/B test allows you to choose the best headline, layout, order button or another element for your web page. You set up a test where you display two variants (A and B) to different website visitors in turns. You wait for a while. It turns out, after 200 visitors, that variant A produced 10 orders out of 100 visitors and the variant B produced 12 out of 100.
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a b testing | google website optimizer