Go and look at the middle school math textbook.

Here is a brief description for everyone.

When some numbers in a set of data are repeated several times, the expression of their average values changes to some extent. For example, if someone shoots ten times, in which 10 rings twice, 8 rings three times, 7 rings four times and 9 rings once, then the average number of rings he shoots is

( 10*2 + 9* 1 + 8*3 + 7*4 )/ 10 = 8. 1

Here, the four numbers 7, 8, 9, 10 are several different ring numbers played by the shooter, but their frequencies are different, which are 4, 3, L and 2 respectively. The greater the frequency of data, the greater the influence on the average value of the whole group of data. In fact, frequency plays a role in weighting data, which is called weight or weight, and the average value above is called weighted average.

In weighted average, besides the frequency of a number in a set of data, weight has a broader meaning.

For example, in some sports competitions, the concept of weight should also be used. For example, in diving competition, each athlete has to complete a certain number of optional movements in addition to the prescribed movements, and the difficulty of optional movements is different. Because of the different difficulty coefficients of the selected movements, the scores of the two players are different, even though the quality of their movements is the same. The higher the difficulty coefficient, the higher the score of athletes, and the difficulty coefficient actually plays a role of weight.

The weights of ordinary arithmetic averages are the same, which are all 1 (for example, the average of 3 and 5 is 4), which means that their importance is the same, so the average is a special weighted average.