The weighted average method of futures index, that is, the value of each futures product is multiplied by the corresponding number of weight units, and then the sum is obtained, and then divided by the total number of units.
The average value depends not only on the tag value (variable value) of each cell in the population, but also on the frequency of each tag value. Because the frequency of each sign value plays a role in measuring its influence in the average, it is called weight.
For example, the following is a classmate's exam results in a certain subject:
Usually take the exam 80, mid-term 90 and final 95.
The calculation method of subject scores stipulated by the school is:
Usually exams account for 20%;
Interim results account for 30%;
Final grade accounts for 50%;
Here, the proportion of each achievement is called weight or weight. So,
Weighted average = 80*20%+90*30%+95*50% = 90.5.
Arithmetic average = (80+90+95)/3 = 88.3
The above example is the case where the weights are known. The following example is the case of unknown weight:
Stock a, 1000 shares, price10;
Stock b, 2000 shares, price15;
Arithmetic average = (10+15)/2 =12.5;
Weighted average = (10x1000+15x2000)/(1000+2000) =13.33.
In fact, when the weight of each number is the same, the weighted average is equal to the arithmetic average.
The reason is the same.