I have a big data set which has about 9000 rows. I have a few variables for every year from 1960 onwards, and I need to average them in ten year bins. So I have something li
Suppose your data starts from A1. Try this one in B1:
=AVERAGE(INDEX(A:A,1+10*(ROW()-ROW($B$1))):INDEX(A:A,10*(ROW()-ROW($B$1)+1)))
and drag it down.
B1 it would be =AVERAGE(A1:A10)B2 it would be =AVERAGE(A11:A20)B3 it would be =AVERAGE(A21:A30)and so on.
General case
If your data starts from An (where n is 2,3,4,...), use this one:
=AVERAGE(INDEX(A:A,n+10*(ROW()-ROW($B$1))):INDEX(A:A,n-1+10*(ROW()-ROW($B$1)+1))
where you should change n to 2,3,4,...