The arithmetic mean is the most common measure of
central tendency. It simply the sum of the numbers divided by
the number of numbers. The symbol

The table, Number of
touchdown passes, shows the number of touchdown (TD)
passes thrown by each of the 31 teams in the National Football
League in the 2000 season. The mean number of touchdown passes
thrown is 20.4516 as shown below.

37 | 33 | 33 | 32 | 29 | 28 | 28 | 23 |

22 | 22 | 22 | 21 | 21 | 21 | 20 | 20 |

19 | 19 | 18 | 18 | 18 | 18 | 16 | 15 |

14 | 14 | 14 | 12 | 12 | 9 | 6 |

Although the arithmetic mean is not the only "mean" (there is also a geometic mean), it is by far the most commonly used. Therefore, if the term "mean" is used without specifying whether it is the arithmetic mean, the geometic mean, or some other mean, it is assumed to refer to the arithmetic mean.