The mean (sometimes also called the arithmetic mean) is the sum of a set of data values divided by the number of data values in the set; in other words, it is the average of a set of numbers.

For example, the mean of 6, 4, and 8 is as follows:

(6+4+8)/3) = 6

Evolutionary biologists find it useful to calculate mean fitness to show the average fitness of a population.