Are the dates really April 2001, what does it say in the formula bar if you
select a cell with Apr-01. The reason I am asking is that if you type in
Apr-01 you will get 4/1/2008 using US date format

If they truly are April 2001 dates and not April 2008 dates and not text
then this will work


=AVERAGE(IF((MONTH(D4:D1000)=4)*(YEAR(D4:D1000)=20 01),F4:F1000))


it needs to be entered with ctrl + shift & enter


replace the cell ranges with your ranges

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Regards,


Peo Sjoblom

"SusanU" wrote in message
...
I have a list of data (about 19000 rows/data values) with water quality
values at 53 locations ranging from March, 1979 through March, 2003. Some
months have 1 value, others have anywhere from 2 to 4. I need helping
coming
up with a formula that will calculate the average, and that I can copy to
the
cell below, for example the average for April, 2001 in cell K250, and the
average for May, 2001 in cell K251.

D E F (value)
465 Apr-01 Salinity 33.5
466 Apr-01 Salinity 29.6
467 Apr-01 Salinity 27.8
468 May-01 Salinity 32.6
469 May-01 Salinity 32.5
470 May-01 Salinity 32.3

Also, I seem to have a hard time grasping how the more complicated
formulas
and arrays work. In spite of hours of reading and trying to understand,
it
isn't intuitive to me. Please bear that in mind when you answer my
question!
Thank you!!