The *mean* is a type of average, giving a measure of the “centre” of a set of data, a random variable or a function. It is obtained by performing a calculation.

There are many different types of mean:

The arithmetic mean is the most common; this is often simply called the “mean”

The geometric mean

The harmonic mean

The root mean square

The power means, which encompass all of the above

The means are significantly affected by outlier values.