Variance  -方差

方差就是一组数据中平均值与任意点之间的距离。

The Variance is the distance between the mean of a set of data to any point in the data. Lets say you have a process whose output are bags whose lengths are

Variation -差异

正常预期结果与观测结果之间的差额总量即为差异

The amount of difference between a normal expected output to the observed output is variation.