Nprinting averages with levels

[markp201]

I understand with multiple levels the sum needs to be divided by 2 (2nd level), 3 (3rd level), etc. 

This works for sums but is it the same for averages?  For example"

Details for group 1 are 2,5,0,9  - group 1 average is 4

Details for group 2 are 15,0,0,5,0 - group 2 average is also 4

The average for group 1 and group 2 is 4 but according to the sum method we would divide this by 2 ?