2010 NCAA RPI--Oct 5 Release

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2010 NCAA RPI--Oct 5 Release

Post by soccerjoy on Tue Oct 05, 2010 10:35 am

The first RPI release has Portland at #2 behind Notre Dame, followed by Stanford, Boston College and North Carolina:

http://web1.ncaa.org/app_data/weeklyrpi/2010WSOrpi1.html

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Re: 2010 NCAA RPI--Oct 5 Release

Post by soccerjoy on Tue Oct 05, 2010 10:59 am

As I am still struggling to understand the intricacy of the RPI, it will be really helpful for me to hear from UPSF or Geez about the connection between this release and the latest nc-soccer.com/wsoccer/2010 release.

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Re: 2010 NCAA RPI--Oct 5 Release

Post by UPSoccerFanatic on Tue Oct 05, 2010 4:38 pm

soccerjoy wrote:As I am still struggling to understand the intricacy of the RPI, it will be really helpful for me to hear from UPSF or Geez about the connection between this release and the latest nc-soccer.com/wsoccer/2010 release.

NC-Soccer produces the unadjusted RPI. The URPI consists of three factors:

Element 1: Team A's winning percentage, computed as (wins + 1/2 ties)/(wins + ties + losses)

Element 2: The average of Team A's opponents' winning percentages against teams other than Team A

Element 3: The average of Team A's opponents' opponents' winning percentages

The URPI formula, which results in the team's rating, is: (Element 1 + (2 x Element 2) + Element 3)/4. Although the ratio given to the Elements is 1:2:1, due to the effective ranges of the Elements (Element 1 has the broadest range, Element 2 a middle range, and Element 3 the narrowest range), the effective weight of the three elements is 50% Element 1, 40% Element 2, and 10% Element 3.

NC-Soccer does not produce the adjusted RPI. What you are seeing in the NCAA report is the teams' rankings based on their adjusted RPIs. The ARPI is computed by adding bonus amounts to teams' URPIs for "good" wins and ties and subtracting penalties for "bad" ties and losses. The bonuses are broken into two groups: wins and ties against teams ranked 1-40 by the URPI; and wins and ties against teams ranked 41-80. Within each of those groups, there 6 possible award amounts -- for wins away (highest bonus), wins neutral, wins home, ties away, ties neutral, ties home. The penalties are broken down similarly into two groups: ties and losses against teams ranked 135-205 by the URPI; and ties and losses against teams ranked 206 and worse. And again, within each of those groups, there are 6 possible penalty amounts -- for ties away (lowest penalty), ties neutral, ties home, losses away, losses neutral, losses home. Thus altogether, there are 12 possible bonus amounts and 12 possible penalty amounts. The bonus and penalty amounts are a closely guarded NCAA secret. I have attempted to figure them out and am fairly close but not right on.

The reason you see Portland at #2 in the NCAA's RPI rankings and at #3 in the NC-Soccer rankings is that Portland has earned enough bonus points to move it from #3 to #2 in the transition from the URPI to the ARPI.

If you want to really know about this stuff, go to the RPI for Division I Women's Soccer website, which I created a couple of years ago. It's chock full of information on the RPI as well as on the NCAA's process for selecting and seeding teams for the NCAA Tournament. It also contains weekly RPI reports that I produce, with the detailed rating information from which the NCAA's RPI rankings are derived. Use the following link and take a look around: https://sites.google.com/site/rpifordivisioniwomenssoccer/

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Re: 2010 NCAA RPI--Oct 5 Release

Post by soccerjoy on Tue Oct 05, 2010 8:11 pm

"I have attempted to figure them out and am fairly close but not right on."

UPSF,

Thank you so much for your explanation. As I compare your latest report (10/3) with the NCAA RPI release, indeed, you are almost right on!

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