I would say that this task is best solved by using a database. Selecting, grouping, averaging, ... are functions found natively in most databases and if you have a mySQL or similar database server lying idle nearby, I should give it a try.

Perl's DBI/DBD combo can be put to good use to import the raw data and then to extract what you need.

CountZero

"If you have four groups working on a compiler, you'll get a 4-pass compiler." - Conway's Law