## 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.

Like this glossary entry? For an in-depth and comprehensive reading on A/B testing stats, check out the book "Statistical Methods in Online A/B Testing" by the author of this glossary, Georgi Georgiev.