Sounds like a job for a pivot table.

Carlos

"Wazooli" wrote in message
...
I have a large data set that has a particular column containing
identifiers.
Here is an example:

RP11-148D23
RP11-148D23
RP11-148F17
RP11-148F17
RP11-148F17
RP11-148F17
RP11-148G20
RP11-148G20
RP11-148G7
RP11-148G7

As you can see, most of the entries in my sheet are duplicates, but there
are several that are repeats of 4, 6 or 8. Each identifier has a
particular
data value assiciated with it. I would like to average across each
identifier, averaging the associated data, but merely pasting down a row
does
not handle the replicates that contain more than 2 or the same kind. Is
there a way to do this conveniently? My spreadsheet contains 13000 rows.