三种平均数：算术平均，几何平均以及调和平均

本文内容截取自该Quora答案

The arithmetic mean：
The arithmetic mean is best used when the sum of the values is significant.

The geometric mean：
The geometric mean is best used when the product of the values is significant.

The harmonic mean：
The harmonic mean is particularly sensitive to a single lower-than average value. (调和平均值对单个低于平均值的值特别敏感。)