In order help answer some questions about the NCAA's Rating
Percentage Index, I'll point out that the NCAA Manual says
3 things are to be considered when selecting teams for the
tournament (all sports):
 
   1. Record
   2. Strength of schedule
   3. Eligibility of athletes
 
I am not sure if it is stated directly (NCAA manual gurus can help
me out here) or just implied, but the idea is that record and
schedule are both equally important in determining which teams
are chosen.
 
Record and Strength of schedule are not precisely defined. OK, record
is pretty easy to figure out. Strength of schedule is not.
 
Personally, since record and SOS are supposed to be equal, I tack
on the constraint of also being "separate". That is, your record
is not based on who you play, just how you do against them. And your
schedule is not based on whether you win or lose, just who you
play.
 
 
The Rating Percentage Index is an attempt to combine record and
strength of schedule into a single number, to make selecting teams
easier.
 
 
And finally, ice hockey has an additional rule (approved by the NCAA,
of course) that lets them consider 4 more criteria in the selection
process: record in last 20 games, head-to-head competition, common
opponents, and record versus other teams under consideration. Note
that all of these criteria are based on a team's record, under different
conditions.
 
 
Keith