Editor's Note - This is a modification of a post I put up on my old Blogger site, updated for the 2009 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 Saturday morning with one based solely on the RPI after Friday night's games (based on info from RealTimeRPI.com).
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, but doesn't provide daily updates. For daily updates, there are a few sites that try to replicate the formula like RealTimeRPI, but most require a subscription for at least some of their data and their update schedules may vary. For example, I checked ESPN's when I started editing this today and it still had an update time of Friday afternoon. I formerly used Ken Pomeroy's listing, until he discontinued it this year. and other statistics while putting my bracket together. He 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 (wins and losses in the last 12 games) 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. St. Mary's, rated 47th in the RPI, became the 34th and final at large teams.
In terms of seeding, I placed the teams in order from 1 to 65 on the S-curve. Pittsburgh (#1) was the top overall seed, and Chattanooga (#177) and Alabama State (#188) 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 and keeping teams teams from the same conference as far apart as possible, at least until the Committee shows us how they will apply their new rules on this).
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
Creighton (11 seed)
UAB (12 seed)
USC (12 seed)
Saint Mary's (12 seed)
In the Full Projection, Out of the RPI Bracket
Arizona (11 seed, 63 RPI)
Boston College (8 seed, 60 RPI)
Maryland (11 seed, 51 RPI)
Penn State (11 seed, 68 RPI)
As you can see, only using the RPI to project the field brings in several teams who are in the at-large conversation (Creighton, Saint Mary's, USC), don't have a great strength of schedule (USC and UAB), and were on the verge of making it in heading into the weekend (USC). In contrast, four teams, all from major conferences, who have good cases (one of whom, BC, is considered a lock by some) are left out.
These changes result in changes to the number of bids for each conference.
Big East - 7 in RPI bracket (7 in full projection)
Big Ten - 7 (8 in full)
Big 12 - 6 (6 in full)
ACC - 5 (7 in full)
Pac 10 - 5 (5 in full)
A-10 - 3 (3 in full)
MWC - 3 (3 in full)
C-USA - 2 (1 in full)
Horizon - 2 (2 in full)
Missouri Valley - 2 (1 in full)
SEC - 2 (2 in full)
West Coast - 2 (1 in full)
Last Four In
First Four Out
Next Four Out
These categories are all based on the RPI. The Last Four In are teams rated 44-47. The First Four Out are rated 48, 49, 51, and 52 (#50 VCU had an auto bid), and the Next Four Out 53, 55, 56, and 57 (#54 Cleveland State had an auto bid).
Most starkly, the RPI led to quite a bit of shuffling in the seeding. This is where teams' performance in their last 12 games and in road and neutral contests would've had the most impact.
Seeding Winners (based on seed line change)
+7 - Siena
+4 - Oklahoma State, Utah, Utah State
+2 - Dayton, San Diego State, Stephen F. Austin, Texas A&M, Xavier
+1 - Butler, Duke, Robert Morris, Syracuse, Tennessee, Western Kentucky
-4 - UCLA
-3 - Gonzaga, LSU, Purdue
-2 - Marquette, Texas
-1 - Arizona State, BYU, California, Clemson, Cornell, Gonzaga, Louisville, Michigan, North Dakota State, Ohio State, Portland State, Temple, Villanova, Wake Forest, Wisconsin
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 a new projection up before the live chat starts at 7 p.m.