Say What? The Amazing NCAA RPI | The Boneyard

Say What? The Amazing NCAA RPI

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triaddukefan

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well you'd better not look at realtimerpi :eek:
 

pinotbear

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http://www.ncaa.com/rankings/basketball-women/d1/ncaa-womens-basketball-rpi

The Huskies are ranked 19th? What am I failing to grasp here?
I am not an RPI maven, but, I suspect that playing Charleston and UCDavis kinda suppresses one's RPI. Vandy, GB, Creighton, and (obviously) Stanford are good, but, at this early point, not enough to offset the aforementioned two. Frankly, given the weakness of the bottom half of the AAC, UConn may not crack the top handful of RPI-rated teams. Now, if you were to just measure out-of-conference schedules, UConn would hold up pretty well.
 
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Green Bay @ #13, South Carolina @ #18 and Notre Dame @ #15 TENN @ # 38 :)
 

cockhrnleghrn

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How about 2-2 MTSU at number 6? What's in the water in Murfreesboro?
 
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The RPI is intended to be an end of the season measure. You need a lot of games played for the results to make sense. It is not useful early in the season at all.



Right. There are always tons of weird rankings early in the year. By later January they will start to make some sense and by year-end they usually are reasonable. Because they don't use score differential, they will never be as reliable as something like Sagarin or Pomeroy. However, for good reason the NCAA doesn't want score differential to be used because it could lead to some really ugly, unsportmanlike games. You might see certain teams pressing late in the game with a 50-point lead and/or never using the end of their bench no matter how large the lead. Even if the margin is capped, there are still a lot of bad scenarios.
 
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The RPI is intended to be an end of the season measure. You need a lot of games played for the results to make sense. It is not useful early in the season at all.
Sorry - gotta disagree. The RPI NEVER makes sense. It's built on a "sounds good" but flawed foundation. Been proven many times over that it's predictive ability of rating two teams against each other is very low. With current schedules, no matter how many games are played, RPI won't get the order of the teams right. (Digging back into the recesses of my brain, pulling out some of my graduate engineering math stuff, I think I might be able to argue that IF every team played every other team exactly once, (a 348 game season!!), then RPI might be be accurate - though I'd have to think on this for a bit)
As far as I know, the purpose of any ratings system (by definition?) is to rank teams - as in the one ranked higher should beat the one ranked lower. RPI fails to do this even late in the season.
 
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Been proven many times over that it's predictive ability of rating two teams against each other is very low.


It is certainly far from perfect, but I think that is an overstatement.
 

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Sorry - gotta disagree. The RPI NEVER makes sense. It's built on a "sounds good" but flawed foundation. Been proven many times over that it's predictive ability of rating two teams against each other is very low. With current schedules, no matter how many games are played, RPI won't get the order of the teams right. (Digging back into the recesses of my brain, pulling out some of my graduate engineering math stuff, I think I might be able to argue that IF every team played every other team exactly once, (a 348 game season!!), then RPI might be be accurate - though I'd have to think on this for a bit)
As far as I know, the purpose of any ratings system (by definition?) is to rank teams - as in the one ranked higher should beat the one ranked lower. RPI fails to do this even late in the season.

I don't think it's true at all that all ratings systems are meant to be predictive.
 

ochoopsfan

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Both USC's are ahead of UConn. Perhaps UConn changes its name to University of Southern Connecticut?
 

Orangutan

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Then what purpose do they serve?

Ranking teams based on what has happened - without trying to guess what will happen.

I would say the selection committee specifically has no interest in a predictive system. It's not their job to guess who would win a specific game or the tournament as a whole. It's their job to decide who the tournament should be set up based on each team's body of work.

RPI is really just a sophisticated version of win-loss records in some ways. It's kind of like how up until Sunday, the Cardinals had the best record in the NFL...but I don't think many people outside of Arizona thought they were the best team in the league. And the underlying statistics bore that out. Just like the underlying statistics bear out that Arkansas really isn't the best team in the country. But I don't think RPI is designed to figure out who the best team is. It's designed to figure out what team has had the best season...and it's meant to be used at the end of the season.
 
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Right. There are always tons of weird rankings early in the year. By later January they will start to make some sense and by year-end they usually are reasonable. Because they don't use score differential, they will never be as reliable as something like Sagarin or Pomeroy. However, for good reason the NCAA doesn't want score differential to be used because it could lead to some really ugly, unsportmanlike games. You might see certain teams pressing late in the game with a 50-point lead and/or never using the end of their bench no matter how large the lead. Even if the margin is capped, there are still a lot of bad scenarios.

That is one of my sore points with college football. These are supposed to be STUDENT athletes, but nothing is learned by beating a team by 70 points.
 
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Sorry - gotta disagree. The RPI NEVER makes sense. It's built on a "sounds good" but flawed foundation. Been proven many times over that it's predictive ability of rating two teams against each other is very low. With current schedules, no matter how many games are played, RPI won't get the order of the teams right. (Digging back into the recesses of my brain, pulling out some of my graduate engineering math stuff, I think I might be able to argue that IF every team played every other team exactly once, (a 348 game season!!), then RPI might be be accurate - though I'd have to think on this for a bit)
As far as I know, the purpose of any ratings system (by definition?) is to rank teams - as in the one ranked higher should beat the one ranked lower. RPI fails to do this even late in the season.
If every team played every other team, everyone's SOS would be approximately the same and RPI would roughly equate to winning percentage. The whole point of RPI is that it compensates for strength of schedule and, to that end, it is a more reliable measure than winning percentage. But it obviously fails when compared with most knowledgeable actual analysis.
 
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Ranking teams based on what has happened - without trying to guess what will happen.

I would say the selection committee specifically has no interest in a predictive system. It's not their job to guess who would win a specific game or the tournament as a whole. It's their job to decide who the tournament should be set up based on each team's body of work.

RPI is really just a sophisticated version of win-loss records in some ways. It's kind of like how up until Sunday, the Cardinals had the best record in the NFL...but I don't think many people outside of Arizona thought they were the best team in the league. And the underlying statistics bore that out. Just like the underlying statistics bear out that Arkansas really isn't the best team in the country. But I don't think RPI is designed to figure out who the best team is. It's designed to figure out what team has had the best season...and it's meant to be used at the end of the season.
Now that the Cardinals' quarterback is out for the year, we don't think that in Arizona either :(
 
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Ranking teams based on what has happened - without trying to guess what will happen.

I would say the selection committee specifically has no interest in a predictive system. It's not their job to guess who would win a specific game or the tournament as a whole. It's their job to decide who the tournament should be set up based on each team's body of work.

RPI is really just a sophisticated version of win-loss records in some ways. It's kind of like how up until Sunday, the Cardinals had the best record in the NFL...but I don't think many people outside of Arizona thought they were the best team in the league. And the underlying statistics bore that out. Just like the underlying statistics bear out that Arkansas really isn't the best team in the country. But I don't think RPI is designed to figure out who the best team is. It's designed to figure out what team has had the best season...and it's meant to be used at the end of the season.
A metric that isn't predictive isn't accurately ranking teams based on their performance. While no system would be 100% accurate, because there are some factors that influence the outcome of games beyond simply past performance (specific match-up advantages, recent injuries, etc.), the more predictive the metric is, the more accurately it is assessing past performance.
 

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A metric that isn't predictive isn't accurately ranking teams based on their performance. While no system would be 100% accurate, because there are some factors that influence the outcome of games beyond simply past performance (specific match-up advantages, recent injuries, etc.), the more predictive the metric is, the more accurately it is assessing past performance.

Part of the issue is that, as discussed above, there are aspects of past performance that the NCAA does not want to assess, namely the scores of games.
 
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So Sagarin's UCONN-ND is ND favored by .81 point after home court is figured in.
Yeah, but it's closer and the ratings are wildly inaccurate based on the few games so far.
Our one loss hit us hard on the ratings, but if you buy into that we learned and have grown far since then, the .81 is immaterial.
I guess i'm saying that the Sagarin allows for us to do better than the RPI does if you put any faith inthese things this early. Also UConn is rated much higher in Jeff's columns than the RPI.
Looking for something positive in the various rating lists. Nothing more. We all know it's about the intangibles right now.
 
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Yeah, but it's closer and the ratings are wildly inaccurate based on the few games so far.
Our one loss hit us hard on the ratings, but if you buy into that we learned and have grown far since then, the .81 is immaterial.
I guess i'm saying that the Sagarin allows for us to do better than the RPI does if you put any faith inthese things this early. Also UConn is rated much higher in Jeff's columns than the RPI.
Looking for something positive in the various rating lists. Nothing more. We all know it's about the intangibles right now.
No faith at all comparing teams where the ratings are that close. I think it does a good job of separating the cream from the next level, etc. And of pointing out that there is not one team with the "cream" all to itself this year. All that matters on Saturday is who plays better.
 
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Part of the issue is that, as discussed above, there are aspects of past performance that the NCAA does not want to assess, namely the scores of games.
Well, put whatever restrictions you want on the data, that doesn't change the fact that, within a given framework, the more predictive model is more accurately assessing past performance.
 
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