# What does "Mu" mean?

Definition of Mu in the context of A/B testing (online controlled experiments).

## What is Mu?

In statistics and probability theory the Greek small letter mu μ is used to denote a population mean or expected value. For example, the expected value of the mean under the null hypothesis would be denoted by μ_{0} while the expected value of the alternative hypothesis will be denoted by μ_{1}. The observed value of mu will be simply μ.

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