How to correctly calculate the average value in a pivot table?

Question

Mathematics

There is a report that unloads information on operators as follows ( https://1drv.ms/x/s!AgFXnBNVCpzbh0bxzvKIygse6Q69?e... ).
That is, the information is unloaded already in the form of an average result for the operator for the selected interval.
The task is as follows: to evaluate the effectiveness of not only the operator, but also the site and the group to which this or that operator belongs.

But if you build the source of the summary not by one unloading, but by several (by dates), then already at the operator level the result for the month will be considered incorrect (because calculations will be made between averaged results), not to mention dropping groups and sites.

Is it possible, based on the available data, to mathematically correctly calculate the average dialogue time?

Answer 1

As far as I understand, you need to display the average for a long period, for several averages with shorter periods. Short periods may not be equal.
Let's say a1, a2, a3 - averages for the 1st, 2nd and 3rd period; n1, n2, n3 - the number of days in each of the periods.
Then the overall average can be found as follows:A = (a1*n1 + a2*n2 + a3*n3)/(n1+n2+n3)