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Tuesday, May 03, 2005

ISR Versus RPI And The Polls

At the suggestion of reader Dave (hat tip), I've added another column to the table I posted here, with the current Iterative Strength Rating (ISR) in the far right column. ISR is an attempt (I think a good one, for the most part) by Boyd Nation of Boyd's World, to correct for the bias I discussed in the RPI. He discusses his ISR ratings here. Here's how it works out:

Team                   RPI  BA  CB  SW/ESPN   ISR

Texas                  1    3   3   2         2
Tulane                 2    2   1   1         4
Miami, Florida         3    5   7   4         17
Baylor                 4    10  11  15        10
Florida                5    6   4   7         15
Mississippi            6    21  25  18        9
North Carolina         7    14  14  9         19
Georgia Tech           8    8   6   6         20
Louisiana State        9    16  13  8         11
College of Charleston  10   NR  26  NR        25
North Carolina State   11   23  NR  NR        32
Oregon State           12   4   9   10        1
Arizona State          13   18  17  22        7
Vanderbilt             14   NR  NR  NR        27
Clemson                15   NR  NR  NR        36
South Carolina         16   19  18  13        18
Cal State Fullerton    17   1   2   3         3
Long Beach State       18   11  10  12        5
Louisiana-Lafayette    19   20  19  16        26
Auburn                 20   NR  NR  NR        47

The ISR gets the unanimous top 3 (in various orders) in the rankings much closer than RPI, with Fullerton, Texas and Tulane all having top 4 ISRs. Miami's #17 ISR is way out of alignment with their 4th, 5th and 7th places in the polls. Included with Miami in the group with RPIs more in synch with the rankings than ISRs - Florida, Georgia Tech, Arizona State and Louisiana-Lafayette (though not by much). Oregon State seems to be a wash, with rankings between 4th and 10th, an RPI of 12, and an ISR of 1. The schools with ISRs more in line with the human polls than the RPIs include: Fullerton, Baylor, North Carolina, College of Charleston, NC State, Vanderbilt, Clemson, Long Beach State and Auburn. Mississippi and LSU are interesting cases...both RPI and ISR give them more credit than the human rankers do.

The results are decidedly mixed. But one thing is clear, especially from the list of teams where ISRs are better aligned with the pollsters. The ISR does, indeed, appear to give more geographically neutral results when compared with the educated human opinion represented in the weekly rankings.

It is equally clear that none of these judgments - RPI, ISR, and the rankings/polls - has any lock on accuracy. But since college baseball doesn't have a balanced schedule, and never will (because of the number of schools, geography, money, etc.), the NCAA selection committee has to make it's own judgments for inclusion in the post-season field, seeding, hosting, etc. They ought to be making comparisons like the above, and others beyond my pay grade, to refine or replace the RPI with a system that eliminates to the extent possible geographic bias (without inserting other biases in its place). Continued slavish adherence to the RPI is no better than sticking their head in the sand.

posted on 5/03/2005 by Jeff Agnew

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