Statistics believes that when calculating indicators such as averages in statistics, the values that have a weighting effect on the values of each variable are called weights.

Example: the average of the following string of numbers

3, 4, 3, 3, 3, 2, 4, 4, 3, 3,

The general method of calculation (3 + 4 + 3 + 3 + 3 + 2 + 4 + 4 + 3 + 3) / 10 = 3.2

weighted method of calculation (6 * 3 * 3 * 4 + 2) / 10 = 3.2

which 3 occurs 6 times, 4 occurs 3 times, and 2 occurs 2 times. 6, 3 and 1 are called weights. This method is called the weighted method.

The average, as it is generally called, is the total number of numbers added up and divided by the total number of these numbers. It is expressed as:

(p1+p2+p3+..... +pn)/n;

But some data records have some of the same data, in the calculation, that a number of the same number of several, multiply this number by a few, this few, called the weight, weighting, is multiplied by a few and then added. The average is still divided by the total number.

Or take the individual numbers above as an example:

Each of them has a few identical numbers, denoted as: k1,k2,k3.......kn;

The formula for the weighted average is: (k1p1+k2p2+k3p3+... . knpn)/(k1+k2+k3+.... .kn)