In A/B testing, it is highly recommended to calculate your visitor sample size before testing. This advice comes from industrial testing practices and is important because it will define the cost of the experiment that we are looking to keep as low as possible.
This is what sample size calculators are used for. You are asked for the current success rate (conversion rate) and the size of the minimum effect to be measured. The result of the calculation is the size of the sample needed to conclude from such an experiment.
This transposes badly in the “digital area” for three main reasons:
- Measuring conversions costs nothing (unlike in the industry).
- The number of visitors is a part of the problem (not the answer).
- The effect of variation is difficult to predict (in practice this is precisely the question you are asking yourself!).
This makes it very difficult to use sample size calculators. So, we have developed a MDE or Minimum Detectable Effect calculator. Just enter the number of visitors you have on your website and the conversion rate of the page you want to test and let the magic happens…
How many users do you need?
Sample size calculator
Calculate how long you need to run an A/B test
and how much traffic do you need to achieve statistically significant results.
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