Editor's Note - This is a modification of a post I put up at about this time last year, updated for the 2010 season.
R, P, and I. Probably the three letters that are thrown around the most during the first half of the month of March in the United States. While everyone is familiar with the term RPI, not everyone knows what it is and how much influence it actually has in the selection process for the NCAA men's basketball tournament. In this post, I'm going to show you how using the RPI alone would give the committee an inaccurate picture of the national landscape and would result in a radically different tournament field than a more balanced selection process would ensure. To do this, I'm going to compare the bracket I released Friday morning with one based solely on the RPI after Thursday night's games (based on info from StatSheet.com).
After the jump, I'll talk a bit more about this unique projection.
What is the RPI?
RPI stands for Ratings Percentage Index, a formula used by the NCAA to rate teams in various sports as a tool in the selection and seeding process for national championships. By nature, the RPI is not a basketball-specific formula, but since the actual formula used in each sport is secret, it can be assumed that each sport's committee makes tweaks to it to match their sport's particular characteristics. For example, since home court advantage is particularly important in basketball, it's pretty well known that there is a penalty built into the basketball RPI for losing at home.
The NCAA releases an official RPI list on Mondays during the season, and it looks like they may finally be updating it daily at the end of the season. For daily updates, there are a few sites that try to replicate the formula like StatSheet, but many of these require a subscription. I formerly used Ken Pomeroy's listing, until he discontinued it before last season in favor of his own (and in my opinion, superior) ratings. and other statistics while putting my bracket together. Pomeroy summarized the basic RPI formula in this way:
"1/4*(Winning Percentage) + 1/2*(Opponents' Average Winning Percentage) + 1/4*(Opponents' Opponents' Winning Percentage)."
He offers a more detailed explanation here.
The RPI does a fair job of measuring a team's performance and even their strength of schedule. However, this doesn't mean it can't be exploited. When building a non-conference schedule a school can schedule games that they should easily win (boosting the 25% winning percentage portion of the formula) against teams who should play well in weaker conferences (boosting the 50% opponents' winning percentage portion while not causing too much harm to the 25% opponents' opponents' portion).
A high RPI rating can tell you if a team can win, it just can't quite tell you the types of teams that it's beating. The separate Strength of Schedule (SOS) rating does this, which is why, more often than not, you'll see a good sized disparity between a team's RPI and SOS.
The RPI formula also doesn't give easy access to two factors that are important in the selection process, recent performance (not necessarily over the last 12 games, as the Committee has de-emphasized a specific timeframe) and road and neutral performance. These are two factors that selection committee members must access and consider during the process.
To create this bracket, I simply selected the 31 teams who had clinched their conference's bid or were the highest remaining seed in their league tournament as my automatic bids. Next, I took the top 34 teams in the RPI who weren't conference leaders to fill in the at-large spots. Virginia Tech, rated 49th in the RPI, became the 34th and final at-large entrant.
In terms of seeding, I placed the teams in order from 1 to 65 on the S-curve. Kansas (#1) was the top overall seed, and Winthrop (#167) and Arkansas-Pine Bluff (#191) were the two teams selected to play in the Opening Round game. I did have to make a few adjustments to the actual bracket to meet bracketing principles (particularly avoiding regular season rematches, keeping teams from the same conference as far apart as possible, and ensuring BYU plays a Thursday/Saturday schedule.
Here are some of the key differences between the two brackets, starting with who's in and who's out.
In the RPI Bracket, Out of the Full Projection
Rhode Island (10 seed)
UAB (11 seed)
Kent State (11 seed)
Dayton (12 seed)
Wichita State (12 seed)
In the Full Projection, Out of the RPI Bracket
UNLV (8 seed, 51 RPI)
Notre Dame (9 seed, 53 RPI)
Florida (10 seed, 52 RPI)
Mississippi (12 seed, 55 RPI)
Illinois (12 seed, 77 RPI)
As you can see, only using the RPI to project the field brings in several teams who are in the at-large conversation (Rhode Island, Dayton) or looked to be finished after losses in their conference tournaments (UAB, Kent State, Wichita State). In contrast, four teams, all from major conferences, who have good cases (two of whom, UNLV and Notre Dame, are considered locks by many at this point) are left out.
These changes result in changes to the number of bids for each conference.
ACC: 7 in RPI bracket (7 in full bracket)
Big East: 7 in RPI bracket (8 in full)
Big 12: 7 (7 in full)
A-10: 5 (3 in full)
Big Ten: 4 (5 in full)
MWC: 3 (4 in full)
SEC: 3 (5 in full)
C-USA: 2 (1 in full)
MAC: 2 (1 in full)
MVC: 2 (1 in full)
Pac-10: 2 (2 in full)
WCC: 2 (2 in full)
Last Four In (RPI in parentheses)
Wichita State (46)
Virginia Tech (49)
First Four Out (RPI in parentheses)
Cornell (50) and Oakland (54) had automatic bids
Notre Dame (53)
Next Four Out (RPI in parentheses)
Seton Hall (56)
William & Mary (59)
Most starkly, the RPI led to quite a bit of shuffling in the seeding. This is where teams' performance at the end of the season and in road and neutral contests would've had the most impact.
Seeding Winners (based on seed line change)
+5: San Diego State
+4: California, Siena
+3: Baylor, Georgetown, Northern Iowa, Old Dominion, Texas, Utah State
+2: Butler, Oklahoma State, Texas A&M
+1: Georgia Tech, North Texas, Oakland, St. Mary's, Wake Forest, Xavier
-5: Marquette, Ohio State, Virginia Tech
-4: Michigan State
-3: Clemson, Gonzaga
-1: Akron, BYU, Florida State. Missouri, Purdue, Richmond, Syracuse, Tennessee, UTEP, Vanderbilt, Vermont
Notice the high number of teams that dropped just one line. Keep in mind that the committee is free to move a team up or down a seed line to protect bracketing principles. This was something I did my best to avoid in this case, since I wanted to try to make this bracket as RPI-based as possible.
I'll have my next projection up Saturday morning.