Weighted average over multiple years

statistics

If I have five years of data each with the number of employees in each department along with the minimum salary (see below), I know I can do a standard weighted average for each year; however, what if I want to do an average minimum salary for the whole five years? Would I do a weighted average of each year independently and then do a simple average of the weighted averages, or would I have to do a weighted average of the weighted averages? Also, what if I wanted to do it by department per year as well? Would I use the number of employees and minimum salary for each year to do the weighted average?

The data for one year looks like this:

Department Min Salary
118 25,834
375 22,356
235 26,519

Best Answer

The order does not change anything you can either

  • Compute the weighted average in one year. Then take the five average, sum them and divide by 5.
  • For each department average over the five years, and then do a weighted average over the departments.
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