Hello, Elena!
You wrote on Wed, 24 Jan 2007 07:11:00 -0800:

E Now it is a little bit more clear to me.

E But what is the right number in this situation?

I would say that you should still calculate your group averages
if you want; they have their uses. However, calculate the
overall average by selecting *all* the data in all the groups.
AVERAGE() is very fast!

James Silverton
Potomac, Maryland

E-mail, with obvious alterations:
not.jim.silverton.at.comcast.not