Webmasters Stack Exchange is a question and answer site for pro webmasters. Join them; it only takes a minute:

Sign up
Here's how it works:
  1. Anybody can ask a question
  2. Anybody can answer
  3. The best answers are voted up and rise to the top

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?

share|improve this question
up vote 8 down vote accepted

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.

share|improve this answer
+1 Thanks @Nick. – Philippe May 26 '11 at 10:36

Your Answer


By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.