Generally speaking, variance is a standard to measure the degree of dispersion of a series of data.

The calculation method is: first find the average value S of data, and then divide the sum of squares of the difference between each data and the average value by the number of data to get the variance.

Variance S=[(x 1-s) square +(x2-s) square +(x3-s) square +...]/n

N is the number of data.