Arithmetic average refers to the sum of all data in a set of data divided by the number of data. It is an indicator reflecting the trend of data concentration.

The formula is:

Average value =(a 1+a2+…+an)/n

For example:

The average of 3, 4 and 5 is:

(3+4+5)/3=4

geometric mean

geometric mean

The nth arithmetic root of product of n positive real numbers. Given n positive real numbers a 1, a2, ..., an, its geometric average is (a1* a2 * ... * an) (1/n). In particular, the geometric average of two positive numbers A and B, C = (a * b) (1/2), is the average of the ratio of A to B. any n positive numbers a 1, a2, ..., An is not greater than the arithmetic average of these n numbers, that is, (a1* A2 * ... *.

Harmonic average

The harmonic average is an average. But statistical harmonic mean is different from mathematical harmonic mean. In mathematics, harmonic average and arithmetic average are independent and self-sufficient. The calculation results are different, and the former is always smaller than the latter. Therefore, the mathematical harmonic average is defined as the reciprocal of the average of reciprocal values. But the statistical weighted harmonic average is different. It is a deformation of the weighted arithmetic mean, which is attached to the arithmetic mean and cannot be established independently. And the calculation result is completely equal to the weighted arithmetic average. It is mainly used to solve the problem that when the total number of units (frequency) cannot be mastered, only the variable value of each group and the corresponding total number of symbols are needed, and the average value is required.

The formula is: 2/( 1/a+ 1/b)

weighted average

If n numbers x 1, x2, ... ……xn are w 1, w2, ... wn, then the weighted average of these n numbers is (x1w/+x2w2+...+xnwn)/(w/kloc). ...

Note: 1) The English word "weight" means the importance of data. In other words, the ability of data reflects the relative "importance" of data.

2) Arithmetic average is a special case of weighted average, that is, when the weights of each item are equal, the weighted average is arithmetic average.

mean square value

The formula is: m = [(a 2+b 2+c 2+… n 2)/n] 1/2.