When running A/B tests with Google Website Optimizer, Google tells you when a variation has "won". However, sometimes, the test runs for a long time and still there is no winner.

When should one decide that there is no significant difference between two variations and stop the test?


The Visual Website Optimizer blog has an A/B test duration calculator designed to answer your question. It's published as an Excel spreadsheet, but don't let that put you off.

Enter your original conversion rate, the difference you're hoping to detect, the number of variations you're testing, and your average daily traffic, and it spits out the number of days you should wait before stopping the test.


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