Why the large discrepancy between Pomeroy and other RPI sites?

[brewcity77]

So I used the 2010 tournament field to see.  And I have to admit that I was surprised by the findings.  Given the conventional wisdom that RPI is flawed, nowhere near as accurate, the committee doesn't use it, they give other ratings more credence, etc. etc. etc., I really thought there would be a significantly greater correlation between the Pomeroy rank and the actual seed received by a team.  I thought the performance of the RPI would be significantly worse than it was.

I guess I shouldn't be surprised anymore that the general response seems to be "don't bother us with the facts."

I for one was glad that you took the time to do that research. I think that it did a good job of indicating that when it comes to Selection Sunday, RPI was slightly more accurate last year than Pomeroy, but more important, that RPI is just as useful an indicator of predicting a team's seed than Pomeroy.

I think that the difference is that most people feel Pomeroy does a better job of saying which team will actually win on the court. And they may be right. I'd be curious to see how RPI and Pomeroy did when it came to head-to-head tourney matches. My guess is Pomeroy would be more accurate in terms of predictions. However, that was never part of your argument, and is another discussion for another day. The bottom line is that while people may dismiss RPI when it comes to results, they certainly shouldn't dismiss it when it comes to inclusion and seeding in March.

[Hards Alumni]

What did you fix?  Anything? 

I find it interesting that you supposedly "fixed" the only post in which someone used actual facts rather than gut feel.

Apparently, you have some issue with the way I made the comparison, but as far as I can tell you neither identified any inaccuracy in the method used, nor did you offer any alternative or suggestions that might improve the accuracy.


The RPI isn't updated after the final conference tournament games.

And since the subject was predicting how accurate the ranking system was with respect to predicting tournament bids and seeds, the fact that RPI doesn't include those games is helpful.

But that was precisely the point--whether one is better than the other at predicting seed.  People are making unsubstantiated claims that Pomeroy is more accurate with respect to predicting who gets in the tournament and where they'll be seeded. 

The reality is that Pomeroy appears to be no better than RPI when it comes to predicting seed.. 


RPI is no longer updated after the the final confernece tournament games.

I don't know if Pomeroy updates to include CNAA tournament games.

I wasn't attacking you.  I was attacking the poor construction of your conclusion.  Sorry, I am a nit-picker.

[Marquette84]

I wasn't attacking you.  I was attacking the poor construction of your conclusion.  Sorry, I am a nit-picker.

Sorry--seemed like you were trying to criticize the work itself simply by emphasizing the person that did it.

I for one was glad that you took the time to do that research. I think that it did a good job of indicating that when it comes to Selection Sunday, RPI was slightly more accurate last year than Pomeroy, but more important, that RPI is just as useful an indicator of predicting a team's seed than Pomeroy.

I think that the difference is that most people feel Pomeroy does a better job of saying which team will actually win on the court. And they may be right. I'd be curious to see how RPI and Pomeroy did when it came to head-to-head tourney matches. My guess is Pomeroy would be more accurate in terms of predictions. However, that was never part of your argument, and is another discussion for another day. The bottom line is that while people may dismiss RPI when it comes to results, they certainly shouldn't dismiss it when it comes to inclusion and seeding in March.

Thank you.

When I have time I'll check a few years back and see if the results are similar for determining field & seed.