Calculation of a running mean

[Guest]

I use a spreadsheet to record test scores - 12 per year. I want to have a
cell where the mean test score is calculated on a running basis - so if there
are 2 tests entered the mean of the two is displayed, 3 testst enetred the
mean of the three is displayed, and so on. Yesterday I received the
suggestion that I use =AVERAGE(Cell addresses), but when I try that it cannot
cope with the empty cells which are for test scores that have yet to be
inputted. Is there a way of doing this?

I am using Excel 2003 and don't have access to the additional statistics
package.

 

[Guest]

With the test scores in A1 - A12 try this:-

=SUM(A1:A12)/COUNTIF(A1:A12,">0")

Mike