Are the RPI Rankings An Accurate Measure of Basketball Team Strength?

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February 20th, 2011 at 12:07 AM
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mGrowOld
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Are the RPI Rankings An Accurate Measure of Basketball Team Strength?

Everybody knows that the sacred RPI rating plays a huge role in determining who is tournament selection worthy and who is not. As of now Michigan is ranked 61st in the most current RPI rankings.  The Belmont Bruins are ranked 53rd with their impressive 24-4 record built by playing THIS schedule:

 

M …
Date Opponent Opp. RPI Rk Results
  11-16   at  Tennessee  16-10 (6-5) 26  76-85  L
  11-17   vs  Arkansas St.  12-14 (8-5) 203  93-60  W
  11-22   vs  Marist  4-24 (3-13) 313  102-74  W
  11-23   vs  Winthrop  10-14 (8-8) 198  71-44  W
  11-29   at  Tennessee St.  9-15 (8-8) 222  87-72  W
  12-02     Mercer  12-15 (10-7) 246  89-67  W
  12-04   at  Vanderbilt  19-6 (7-4) 14  76-85  L
  12-07     Middle Tenn. St.  13-13 (9-5) 197  88-87  W
  12-16     Kennesaw St.  7-19 (6-11) 324  87-60  W
  12-18   at  Troy  7-17 (6-7) 249  98-63  W
  12-20   at  Alabama St.  7-16 (6-6) 320  66-53  W
  12-23   at  Tennessee  16-10 (6-5) 26  65-66  L
$  12-30     Miami (OH)  13-12 (9-3) 97  83-72  W
  01-03   at  Fla Gulf Coast  6-19 (3-12) 298  83-51  W
  01-05   at  Stetson  7-20 (5-12) 301  70-53  W
  01-08     North Florida  10-18 (7-10) 172  91-59  W
  01-10     Jacksonville  17-8 (12-5) 116  81-50  W
  01-13     Lipscomb  15-10 (11-6) 110  88-52  W
  01-15     Campbell  11-15 (6-11) 252  90-55  W
  01-21   at  South Carolina-Upstate  4-23 (3-14) Mm 317  67-62  W
$  01-23   at  E. Tennessee St.  18-10 (14-4) 100  72-62  W
?  01-25   at  Lipscomb  15-10 (11-6) 110  64-73  L
  01-28     Fla Gulf Coast  6-19 (3-12) 298  89-56  W
  01-30     Stetson  7-20 (5-12) 301  82-64  W
  02-03   at  Jacksonville  17-8 (12-5) 116  76-70  W
  02-05   at  North Florida  10-18 (7-10) 172  69-67  W
  02-12   at  Campbell  11-15 (6-11) 252  78-57  W
$  02-17     E. Tennessee St.  18-10 (14-4) 100  68-58  W

Look at the RPI rankings of their vanquished foes.  How is it possible that beating this collection of cupcakes garners a team an RPI ranking higher than ours?  What is wrong with this picture?????

And did they really play Tennessee twice?

 

 

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February 20th, 2011 at 12:12 AM | RPI seems (Score:1)
swaglikeM
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Joined: 11/02/2009
MGoPoints: 187

just like the BCS rankings nobody knows really how they're calculated they just accept them..

February 20th, 2011 at 12:45 AM | It's actually a very simple formula (Score:1)
Muttley
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albeit with a lot of data behind it.

RPI = (WP * 0.25) + (OWP * 0.50) + (OOWP * 0.25)

where WP is Winning Percentage, OWP is Opponents' Winning Percentage and OOWP is Opponents' Opponents' Winning Percentage.

Or if you prefer, see Ken Pomeroy's summary

I am almost certain one could find a measure that provides a better predictor of future wins. Nonetheless, Ken Pomeroy defended it here (scroll way down to see beginning of the post long ago in comparison to the early BCS methodology, which kept USC out of the title game in 2003

And considering its simplicity, the RPI is pretty good at what it's supposed to do. Winning games is good, playing a tough schedule is good. But more fundamentally, just being a good team is good. There’s really no easy way to cheat the system. And even if you could, there is a bunch of humans waiting at the end of the season to try to smooth out the problems.

Posted on 12/26 at 01:20 AM

February 20th, 2011 at 12:50 AM | Beat me to it. (Score:1)
BJNavarre
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Beat me to it.

February 20th, 2011 at 12:51 AM | I should have added (Score:1)
Muttley
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A home win now counts as 0.6 win, while a road win counts as 1.4 wins. Inversely, a home loss equals 1.4 losses, while a road loss counts as 0.6 loss. A neutral game counts as 1 win or 1 loss. Note that this location adjustment applies only to the WP factor and not the OWP and OOWP factors. Only games against Division 1 teams are included for all RPI factors.

February 20th, 2011 at 12:59 AM | posted from iPhone (Score:1)
goblueritzy92
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Why is the multiplier for winning % .25 while the opponents winning % is .5?

February 20th, 2011 at 1:11 AM | Variance (Score:1)
Alton
Joined: 07/05/2008
MGoPoints: 978

Because winning percentage varies much more than opponents' winning percentage.

For example, the best teams have a winning percentage of about .900, the worst have winning percentages of about .100.  Opponents' winning percentage only varies from about .400 to about .600.  So the best teams get (.900 x .25) = .225 RPI points for their winning percentage and the worst teams get (.100 x .25) = .025 RPI points for their winning percentage.  About a .200 difference between the best and worst teams.

But in opponents' winning percentage (OWP), the teams with the strongest schedules get (.600 x .5) = .300 RPI points for their OWP, and the teams with the weakest schedules get (.400 x .5) = .200 RPI points for their OWP.

So even though the factor for winning percentage is only .25 and the factor for opponents' winning percentage is .50, really the difference between the best and worst teams is about twice as big for winning percentage compared with OWP.  You  could say that winning percentage is weighted about twice as heavily as opponents' winning percentage, when variance is taken into account.

February 20th, 2011 at 1:44 PM | Logged in just to upvote you. (Score:1)
tjyoung
Joined: 08/23/2009
MGoPoints: 189

Logged in just to upvote you.  Extremely good post.  Very well thought-out and explained.  Thank you.

February 20th, 2011 at 12:52 AM | The RPI is actually a really (Score:1)
BJNavarre
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The RPI is actually a really dumb formula that is intentially dumbed down so that most people who care to learn the formula can easily understand it.

What they should actually shoot for is a ratings index that is the best predictor of future results based on wins and losses alone. This would require lots of fancy math and statistics, so it's not going to happen. The NCAA prefers a system that slaps randomly chosen factors to opponents and opponents-opponents win-loss record because it's easy to compute.

February 20th, 2011 at 1:15 AM | Ahead of its time (Score:1)
Alton
Joined: 07/05/2008
MGoPoints: 978

Exactly--the big problem is that RPI was created in the late 1970s, about 5-10 years before home computers became ubiquitous.  It was therefore determined that a linear calculation was preferable, rather than a matrix-based or iterated calculation, even though the math makes much more sense with a matrix-based formula.

So the real problem is that they had to use a suboptimal approach to rating, in order to appease the athletic department people who wanted to be able to check the NCAA's math without using a computer.

February 20th, 2011 at 1:51 PM | Not necessarily (Score:2 Normal)
Seth9
Joined: 04/01/2009
MGoPoints: 2336

The best predictive systems often rate teams higher than they deserve to be based on their actual accomplishments. For instance, Sagarin's post-national championship game predictive system ranks Auburn 5th, even though they won the national titile. Alabama, by contrast, is ranked 3rd. Oregon is ranked 2nd, and Stanford is ranked 1st. In college basketball, Kenpom ranks Clemson 38th, despite their middling schedule, a few poor losses, and their best win coming over #40 FSU. The reason for both of these oddities is that Clemson and the teams ranked above Auburn lost relatively close games and won a number of games by wide margins. This is important because margin of victory or defeat is generally a better predictive measure than who actually wins or loses a game.

This is a problem area when deciding who is actually more deserving of a tournament spot. On one hand, it is obviously better to beat a team by 20 than to beat them by 2. On the other hand, if Team A wins beats two teams by a margin of 5 points apiece and Team B beats one of them by 15 and loses the other by 1, I doubt anyone would say that Team B is more deserving of a bid than Team A as the ultimate goal in team sports is to win, and the margin of a victory is a secondary concern.

February 20th, 2011 at 12:19 AM | I've recently lost all faith in it (Score:1)
Erik_in_Dayton
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Joined: 12/03/2008
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A friend and I were noticing things like you did just a few days ago.  The RPI rankings are full of oddities like that. 

It's tough to make predictions, especially about the future. -- Yogi Berra

                         

February 20th, 2011 at 12:22 AM | Don't look at Kenpom (Score:1)
Michigan4Life
Joined: 07/29/2010
MGoPoints: 5662

They have Belmont at #31.

 

KenPom is a better ranking because they strip it down to tempo free stats IMO.

February 20th, 2011 at 12:27 AM | It was probably because of (Score:1)
mGrowOld
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It was probably because of their big win over Kennesaw State. All great teams need a signature win and you simply can't take that on away from the mighty Belmont Bruins.

 

 

February 20th, 2011 at 12:39 AM | KenPom rankings (Score:1)
Michigan4Life
Joined: 07/29/2010
MGoPoints: 5662

take account into strength of schedule.  With that being said, if you dominate your competition, you deserve to be ranked high at #31 which Belmont is.


They blew out most of the teams in their schedule which is why they're 24-4 and is a favorite to win Atlantic Sun conference.

February 20th, 2011 at 12:27 AM | It helps when you win nearly (Score:1)
MH20
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It helps when you win nearly every game you play.

"The difference between a man and a boy is, a boy wants to grow up to be a fireman, but a man wants to grow up to be a giant monster fireman."

- Jack Handey

February 20th, 2011 at 12:29 AM | It's certainly not everything (Score:1)
wlubd
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It's certainly not everything but it works as a basic indicator. The key with RPI is that you really need to look at SOS at the same time.

Michigan- RPI: 61 SOS: 18

Belmont- RPI: 53 SOS: 230

So yes, Belmont has a slightly better RPI but the SOS has to be considered. If resumes were based on this alone, Michigan would far and away be more impressive.

Twitter

February 20th, 2011 at 11:09 AM | wisky (Score:1)
umchicago
Joined: 02/05/2009
MGoPoints: 3531

this is why the wisky game is so important.  a W would mean a decent jump in rpi.  our strength of schedule will also jump after the final 3 games.

that said, the rpi is too simplistic a formula.  at least the BCS considers several formulas to attempt to eliminate any strange bias of a single formula.

February 20th, 2011 at 1:17 AM | RPI is a relatively simple formula (Score:1)
Seth9
Joined: 04/01/2009
MGoPoints: 2336

For college basketball, here is how you calculate RPI:

RPI = Winning Percentage * 0.25 + Opponents' Winning Percentage * 0.5 + Opponents' Opponents' Winning Percentage * 0.25.

Winning percentage is adjusted for road and home advantages. Home wins count as 0.6 wins, home losses count as 1.4 losses, road wins count for 1.4 wins, road losses count for 0.6 losses. Neither opponents' winning percentage nor opponents' opponents' winning percentage is calculated with this adjustment.

Opponents' winning percentage is also adjusted to remove any games you play. So if you beat a team, you do not reduce your opponents winning percentage for the purpose of the RPI. Opponents' opponnents' winning percentage, on the other hand, does not remove any games from consideration.

The reason that Belmont's RPI is higher than Michigan's (albeit very slightly) is simple. While Belmont has faced a weak schedule, their winning percentage as calculated by the RPI is very high as they have played a lot of games on the road and won a lot of them too. Meanwhile, they have home losses to drag down their winning percentage.

The biggest issue with the RPI, in my opinion, is that it does not care whether you have any quality wins. That is why the NCAA considers quality wins an additional item to consider alongside RPI when deciding who goes to the tournament.

February 20th, 2011 at 1:28 AM | Change "Are" to "Is" so you (Score:1)
LarryHarrison
Joined: 12/04/2010
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Change "Are" to "Is" so you don't look like a dumbass.

February 20th, 2011 at 1:34 AM | Coming from a guy who proudly (Score:1)
UMICH1606
Joined: 02/21/2010
MGoPoints: 1861

Coming from a guy who proudly stalks players and recruits on the internet?

February 20th, 2011 at 2:21 AM | I'd hate to hear what you (Score:1)
LarryHarrison
Joined: 12/04/2010
MGoPoints: 227

I'd hate to hear what you have to say about Tim. This site really is full of morons. I'll keep posting to even it out with my supreme intellect.

February 20th, 2011 at 6:39 AM | Why thank you for the (Score:1)
mGrowOld
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Why thank you for the excellent grammar tip. I appreciate you looking out for me.

But weren't YOU the guy yesterday accusing me of belittling other posters and generally feeling superior to other people? How ironic.

 

 

February 20th, 2011 at 8:39 AM | or in his case (Score:1)
MGoSoftball
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moronic

From the Red Cedar Message Board:  "God hates us."  Yes He does Lil Bro, yes he does.  Everyone hates you.

February 20th, 2011 at 2:46 PM | The level to which you took (Score:1)
LarryHarrison
Joined: 12/04/2010
MGoPoints: 227

The level to which you took it can not be put in the same category. You ARE an epic douche.

February 20th, 2011 at 5:42 PM | Hey Larry.... I've got (Score:1)
mGrowOld
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Hey Fuckwad.....I mean Larry:

I've sat quietly and taken your shit long enough.  I'm not quite sure which one of the politically correct edicts I broke to so incur your rightious indignation but I've had enough of it.  So here's a summary of the score to date:

I've got three kids who love me (the most important thing I have).  I would be shocked if you had any clue what fatherhood was like

I've got a far better job than you (own my own company with 250+ employees and are moving forward with an IPO in spring 2012)

I've got way cooler toys than you (just bought a CTS-V yesterday...it's awesome)

I've got a WAY hotter wife than you who also loves me (see my avatar for proof)

I've got lots of friends

I am actively involved in my church, serve on three charitable boards and go to inner city Cleveland Sunday nights to feed the homeless.

So while I cant speak for the entire board I guess I do think i'm better than you.  Go fuck yourself Larry or Busey or whatever the hell you call yourself.

 Truth is a bitch asshole.

 

 

February 20th, 2011 at 7:48 PM | LOL U MAD? (Score:1)
poguemahone
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The current state of MGoBoard distilled into one perfect post. 

EVERYONE

 

GET OUT YOUR RULERS AND UNZIP YOUR PANTALOONS

 

IT'S MEASURING TIME

February 20th, 2011 at 7:50 PM | What if you're all grow and (Score:1)
ShockFX
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What if you're all grow and no show?

February 20th, 2011 at 7:55 PM | I just realized what this reminds me of (Score:1)
poguemahone
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Hey Faggots, My name is John, and I hate every single one of you. All of you are fat, retarded, no-lifes who spend every second of their day looking at stupid ass pictures. You are everything bad in the world. Honestly, have any of you ever gotten any pussy? I mean, I guess it's fun making fun of people because of your own insecurities, but you all take to a whole new level. This is even worse than jerking off to pictures on facebook.

Don't be a stranger. Just hit me with your best shot. I'm pretty much perfect. I was captain of the football team, and starter on my basketball team. What sports do you play, other than "jack off to naked drawn Japanese people"? I also get straight A's, and have a banging hot girlfriend (She just blew me; Shit was SO cash). You are all faggots who should just kill yourselves. Thanks for listening.

http://encyclopediadramatica.com/So_cash#The_Original_Cash

February 20th, 2011 at 7:59 PM | I was 6th man in basketball.  (Score:1)
mGrowOld
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I'm tired of taking that idiots shit.  Sue me.

 

 

February 20th, 2011 at 8:01 PM | If you were my boss, I'd quit (Score:1)
ShockFX
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Joined: 07/16/2008
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If you were my boss, I'd quit my job. Just sayin'

February 20th, 2011 at 8:06 PM | I'll be you wouldnt.  We run (Score:1)
mGrowOld
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I'll bet you wouldnt.  We run an inside sales department and the average income is 90k.  If you quit you'd be the first.

 

 

February 20th, 2011 at 8:12 PM | You do understand that your (Score:1)
ShockFX
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Joined: 07/16/2008
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You do understand that your awesomeness does not preclude others using this awesome thing called the internet from also having awesomeness correct?

February 20th, 2011 at 8:47 PM | My post wasn't directed at (Score:1)
mGrowOld
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My post wasn't directed at you so I'm not quite sure how it managed to offend you unless you're Larry. He has made several disparaging remarks about me as a person and in real life I do kick his ass. I made zero claims to be more awesome than one guy.

 

 

February 20th, 2011 at 8:00 PM | I DRIVE A DODGE STRATUS! (Score:1)
Dreisbach Turne...
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I DRIVE A DODGE STRATUS!

Syracuse '03, Michigan G'05

Space bitches, space.

February 20th, 2011 at 7:23 AM | Whoa, I was unaware that Rush (Score:1)
UMHopeful_in_NY
Joined: 02/14/2011
MGoPoints: 19

Whoa, I was unaware that Rush Limbaugh was roaming the MGOBoard.

University of Miami (FL) class of 2015

February 20th, 2011 at 1:30 PM | "Full of morons?" (Score:1)
Tater
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Wow, Larry.  You certainly have come a long way from the days when you were the guy with the "morans" sign.  Congrats on your "supreme intellect."

 

 

 

February 20th, 2011 at 2:44 PM | Link? (Score:1)
LarryHarrison
Joined: 12/04/2010
MGoPoints: 227

Link?

February 20th, 2011 at 9:09 AM | What? (Score:1)
PeterKlima
Joined: 08/24/2008
MGoPoints: 1424

He pluralized rankings and there are multiple RPI ranks. Now you look like a dumbass.

February 20th, 2011 at 10:08 AM | Correction (Score:1)
Bosch
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Joined: 04/03/2009
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Change "Are" to "Is" so you don't look like a dumbass LarryHarrison.

All right Lemmings. Bring the heat.

February 20th, 2011 at 3:05 AM | +10000 for excellent thread (Score:1)
CoachW
Joined: 01/10/2009
MGoPoints: 450

+10000 for excellent thread title.  All other posters take notice, this is how you title a post. 

February 20th, 2011 at 8:34 AM | Record (Score:1)
Mitch Cumstein
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MGoPoints: 9641

At the end of the day, if you're record is 24-4, you're always going to have a solid computer ranking.  Think of the BCS, undefeated teams are usually very high in the computers regardless of who they've been.   A teams record is always a substantial part of these rankings.

"A flute with no holes is not a flute. A donut with no hole is a danish"

February 20th, 2011 at 10:51 AM | I guess that's my point.  (Score:1)
mGrowOld
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MGoPoints: 13158

I guess that's my point.  Playing cupcake U....and winning....seems to give teams a favorable RPI ranking.  And given that the RPI. not SOS, is the metric most commonly quoted when evaluating a teams tourny chances I'm questioning its validity.  As someone accurately pointed out, our SOS is one of the nation's best (thanks Big 10) yet we are barely mentioned as a bubble team, much less in, because of our poor RPI.

Doesnt seem right to me.

 

 

February 20th, 2011 at 11:43 AM | that team will probably end (Score:1)
Michigan Arrogance
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MGoPoints: 4285

that team will probably end up winning 30 games, including their conf tourney. I'm fine with them having a better RPI than a mediocre M team.

Harvard: The MICHIGAN of the East

We're not arrogant, we're just better.

February 20th, 2011 at 12:09 PM | If at season's end the RPI is (Score:1)
aiglick
Joined: 11/27/2010
MGoPoints: 1440

If at season's end the RPI is sub 50 that will help M's chances. RPI is mentioned a lot but almost always in connection with SOS. Should be an interesting finish to the season.

Here's hoping for a bright future. This team does try hard and I will continue to support them.

February 20th, 2011 at 2:35 PM | As an at-large, Belmont's (Score:1)
cmd600
Joined: 11/17/2010
MGoPoints: 75

As an at-large, Belmont's tourney chances aren't better than Michigan's. The committee likes to use RPI, but not simply as 'team with RPI 57' > 'team with RPI 58'. Record vs top 25 and top 50 teams by RPI matter a lot, and Belmont's 0-3 record vs the top 50 almost certainly keeps them from getting an at-large spot

February 20th, 2011 at 9:46 PM |  And given that the RPI. not (Score:1)
jmblue
Joined: 11/07/2008
MGoPoints: 28961

 And given that the RPI. not SOS, is the metric most commonly quoted when evaluating a teams tourny chances I'm questioning its validity.

SOS is part of the RPI formula.  Our SOS is the reason our RPI is as high as it is.  17-11 probably isn't even one of the 100 best records in the country.

February 20th, 2011 at 11:39 AM | So perhaps we should schedule (Score:1)
ReadYourGuard
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MGoPoints: 6189

So perhaps we should schedule the Oakland U game at their barn in the future.

"the Spirit of Michigan...is based on a deathless loyalty to Michigan and all her ways....and a conviction that nowhere is there a better university, in any way, than this Michigan of ours" - Fielding Yost
February 20th, 2011 at 11:56 AM | Seems to me haven't we played (Score:1)
MH20
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MGoPoints: 7575

Seems to me haven't we played them at the Palace a few times?  I think MSU has, too.

"The difference between a man and a boy is, a boy wants to grow up to be a fireman, but a man wants to grow up to be a giant monster fireman."

- Jack Handey

February 20th, 2011 at 12:00 PM | Stetson? (Score:1)
mooseman
Joined: 07/10/2008
MGoPoints: 393

They played a hat, for god's sake. Well, maybe it was a ten gallon hat. Plus the cologne. Ok, I'm cool with the rating.

February 20th, 2011 at 12:26 PM | Don't forget they played (Score:1)
mGrowOld
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Joined: 10/04/2010
MGoPoints: 13158

Don't forget they played these guys too.....twice.

 

 

 

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