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Frequently Asked Questions
Below is much of what you need to know about the RPI. It is all from an article by Jerry P. Palm of CBS Sportsline.
The source SportsLine
ps Mr. Palm compiled some of his information from data provided by NCAA Senior Statistics Coordinator Gary K. Johnson, keeper of the official RPI.
If you still want to know more, e-mail your questions to Jerry P. Palm at jppalm@collegerpi.com.
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What is the RPI?
The RPI (Ratings Percentage Index) is a measure of strength of schedule and how a team does against that schedule. It does not consider things like margin of victory or where a game is played, only whether or not a team won. It is used by the NCAA as one of their factors in deciding which teams to invite to the NCAA tournament and where to seed them.
It was created and is maintained by the NCAA Division I Men's Basketball Committee. They have always placed a premium on schedule strength when selecting teams for the tournament, so they wanted a relatively simple way to measure that and the RPI was born. This page is an independent duplication of those ratings.
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Just how important is the RPI?
As far as getting into the tournament, it appears to be more important to bubble teams than the top powers. It is also important in the seeding process.
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What is the formula?
The basic formula is 25% team winning percentage, 50% opponents' average winning percentage, and 25% opponents' opponents' average winning percentage.
For example:
- Team A is 5-0, winning pct = 1.000
- Team A's opponents' average winning pct = .600
- Team A's opponents' opponents' average winning pct = .800
Team A's RPI would be (.25 * 1.000) + (.5 * .600) + (.25 * .800) = .250 + .300 + .200 = .750. Not bad.
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Do you adjust the opponents' average winning percentage to account for the fact that they have played the team in question?
Yes. I also make an adjustment for the fact that the team in question is among their opponents' opponents'.
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Does the NCAA make these adjustments too?
Yes.
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In the opponents' average winning percentage, do you include the records of teams scheduled in the future?
No. A team's record is included in the opponents' average winning percentage only after the game is played. This is because a team's entire schedule is not usually known, mostly due to games added because of in-season and conference tournaments. Also, sometimes games get canceled.
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Do you use the record of an opponent at the time the game is played or at the time the RPI is calculated?
The RPI is always calculated based on current records, not date-of-game records.
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If a team plays somebody more than once, is their winning percentage included more than once?
Yes. Once for each time a team plays that opponent.
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What about the NCAA's secret adjustments?
There is an adjustment that the NCAA makes to the basic RPI. They don't say what it is (it's top secret), although it is basically a system of bonuses and penalties. Teams receive bonuses for beating teams in the top 50 of the basic RPI ("good wins") and for scheduling 50 percent of their non-conference games against opponents ranked in the top 50. Penalties are assessed for losing to non-Division I teams, losing to teams ranked 150 or below in the basic RPI ("bad losses") and for scheduling 50 percent of the non-conference schedule against teams ranked 150 or below. There is also some game location factoring in the bonuses for good wins and penalties for bad losses.
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How much difference do the secret adjustments make?
That depends. The adjustments were created to help better measure the "bubble" teams. If teams are tightly packed together in the basic RPI, the adjustments will have a bigger affect than if they are further apart.
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How do you figure a conference's RPI?
It's simply the average of the RPI's of the teams in the conference. The NCAA does this both ways: with and without conference games. I provide both numbers as well, but rank them by non-conference. I feel that conference games are like a team playing itself, so they shouldn't count. It should be noted that this data is among the least relevant in the selection process.
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How do you figure the Strength of Schedule?
It's 2/3 opponents' winning percentage and 1/3 opponents' opponents' winning percentage.
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Why do the rankings seem so weird early in the season?
The RPI is primarily a measurement of strength of schedule and how the team did against that schedule and each season stands on its own. Consequently, the numbers can really skewed early in the season because teams have played so few games. For example, a team can be 2-0, but its opponents haven't played anyone else yet, so its strength of schedule is 0. That's 75% of the formula, so the team won't be rated very highly. The data starts to take shape and look reasonable as conference play gets into full swing around the end of December. And the more games played, the better the data gets.
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Why is my team's record wrong?
The RPI is calculated using games between full-fledged Division I (D-I) opponents only. All 318 full-fledged D-I teams are listed in the rankings. If a school plays a team not listed in the rankings, that game doesn't count and won't be reflected in the records or results.
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