Example:
There are 1, 2, 3, 4 and 5 groups of samples, the average of which is (1+2+3+4+5)/5=3, and the variance is the average of the square sum of the difference between the average of each data and its sum, namely:
[(1-3) 2+(2-3) 2+(3-3) 2+(4-3) 2+(5-3) 2]/5 = 2, and the variance is 2.
Variance formula:
Variance is the average of the square of the difference between the actual value and the expected value, while standard deviation is the arithmetic square root of variance.
Variance is the average of the sum of squares of the difference between each data and the average, that is
Where x represents the sample average, n represents the sample number, xi represents the individual, and s2 represents the variance.
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 S2.