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I am having data of 10 schools, each school is having different no of sections. Each section students attended different no of computer classes. How to calculate the average no of computer classes attended by 10 school students. I tried to calcluated the overall average in following steps. First i calculated average of each school by taking the sum of no of computer classes taken in the school divided by no of sections. in second step, i added all the averages and divided the sum by no of schools(i.e.10). is it correct method. please suggest if anyother method available to solve this problem.

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You should probably multiply each average by the number of students, add them up and deivide by the number of students. If you think about it, this is the total number of classes divided by the total number of students, i.e., the overall average. – vonbrand Mar 28 '13 at 17:19

In general, the average of averages is not the average. This was discussed before: Is the average of the averages equal to the average of all the numbers originally averaged?

The correct method is to undo the averaging over schools, as vonbrand suggested: find the total number of classes taken by the students of each school. Add those numbers together, and divide by the sum of total enrollments of the schools.

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