Variance calculation formula: if the average value of x 1, x2...xn is m, then the variance S2 =1/n [(x1-m) 2+(x2-m) 2+...+(xn-m) 2].

Variance is the degree of deviation from the center, which is used to measure the fluctuation of a batch of data (that is, the degree of deviation from the average value of this batch of data). It is called the variance of this group of data and is recorded as S 2. With the same sample size. The greater the variance, the greater the volatility and instability of the data.