The **arithmetic mean** is defined as the sum of all the members of a set of data divided by the number of items in the set. If the set used is a population, then we speak of the [population mean]?. When the set is a sample, we call the statistic a [sample mean]?.

We denote the set of data by X = {x_{1}, x_{2}, ..., x_{n}}. The symbol µ is used to denote the arithmetic mean of a population. We use the name of the variable, X, with a horizontal bar over it as the symbol for a [sample mean]?. We read this symbol as "X Bar".

- Arithmetic mean = ( x
_{1}+ x_{2}+ ... + x_{n}) / n

see also [geometric mean]?, [harmonic mean]?, weighted mean, variance, central tendency

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