=AVERAGE(IF(MONTH($O$5:$O$200)=1,$P$5:$P$200))

This is for January. Change 1 to 2 for Feb, 3 for March etc.

It is an array formula and needs CTRL+SHIFT+ENTER not just ENTER.




"sarahg" wrote in message
...
Hi

I have a list of numerical values (P5:P200) in O5:O200 is a corresponding
date as to when the values were recorded. How can I calculate an average
of
values collected within a specific month.

Thanks