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Sample size calculator for A/B testing

Sample size & test length calculator

Monthly unique visitors The number of unique visitors that will be included in your test.
Variations plus original Total number of variations including original that is included in the test.
Baseline conversion rate (%) The avarage conversion rate of visitors that will be part of the test. Generally found in Google Analytics.
Minimal detectable effect (%) The miminum increase in the baseline conversion rate that you are looking to detect.

Significance (%)
The probability that the result is not a false positive. Default is 90.
Power (%)
The probability that the result is not a false negative. Default is 80.
Sample size per variation

Total sample size

Estimated time
days

How we calculate

This calculator is used to compute the sample size for your variations and the test length and is based on the SiteGainer Stats Engine which employees the Frequentist methodology known as a one-tailed Z test for the difference between two proportions.

When testing one or more variations, the calculator adjusts the sample size using the Bonferroni correction.

For more information on why we are using one-tail tests, read Common misconceptions about one-tailed vs. two-tailed tests

Need assistance?

Please use our chat or e-mail support@sitegainer.com to get assistance on how to determine your sample size.

Request a SiteGainer demo, start a free trial or chat with us to get in touch.

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Statistics / Funnels

Track and A/B test anything you create in SiteGainer! With our one-tail statistics calculation you get fast and accurate statistics that is easy to use to make informed decisions about which variation should be implemented!

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What really sets us appart is our experience. We have sucessfully launched over 2000 A/B tests for clients world wide and we can assist you with test ideas, design, programming, analytics, and personalization!

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Each one of your websites get a unique script for fast loading A/B tests, and you can have unlimited websites

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With our one of a kind A/B test editor for making popups your can make unlimited popups!

Complex personalization

Change your website in minutes without touching your sourcecode, and target the changes to the right audience!

Easy to use interface

Whether you are making a popup, an A/B test or a banner you will feel right at home, everything works the same!

No coding required

With our A/B test website editors there is no requirement to code!

CSS / jQuery separation

Easily create A/B test variations in pure css or jquery for easy implementation!

Fast script technology

With our unique script algorithm we make your A/B test run long before the page is loaded!

Heatmaps for everything

With mousemove and click heatmaps you can directly see how your A/B test or banners are performing!

Retroactive goals

Add your goals at any time, we got your back! Works for all page goals you want to measure!

Content Targeting & Goals

Want to target or measure content not in the url string, but on the site? No problems!

Only one script

One script: Unlimited A/B tests, customizations, banners and popups.