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NCAA Hockey Rankings

What do these rankings mean? The simplest ranking is a team's record - its winning percentage where a tie counts as half a win and half a loss.

Each team's record counts as 25% of its Rankings Percentage Index (RPI). The team's opponents' winning percentage counts 21%, and its opponents' opponents' winning percentage the other 54%. There is also a "quality wins bonus" for wins against teams in the top 20.

The RPI is one of the components of the Pairwise Rankings (PWR) along with record against common opponents and head-to-head record. The NCAA uses the PWR to determine which teams will participate in the NCAA tournament.

KRACH - the Bradley-Terry System applied to college hockey - is the most mathematically sound way to rank teams. Team A's KRACH divided by Team B's KRACH gives the odds that Team A will defeat Team B. (See also http://www.mscs.dal.ca/~butler/krachexp.htm.)

Once the KRACH ratings are known, it is possible to calculate a Krach PWR. This differs from the standard PWR in three ways. First, KRACH replaces RPI as the first component. Accordingly, the criterion for a team to be under consideration becomes having a KRACH in the top 25. Lastly, the TUC and COP components are "Krachified." (See also http://slack.net/~whelan/tbrw/2000/kpairwise.shtml.)

KASA stands for KRACH Adjusted for Site Advantage. It is an extended Bradley-Terry method that takes home-ice advantage into account.

HEAL differs from the other methods by taking into account not only how many games a team has won, but which opponents they have beaten; RHEAL is a recursive version of HEAL. (See also http://maine.edu/HEAL/.)

E-ratings, developed by Eugene Potemkin, provide yet another ranking system. (See also http://rsport.narod.ru/wwrr/theory/erating.htm and http://www.mratings.com/theory/erating.htm.)

CHODR is unique in that it takes into account the actual score of each game as well as home-ice advantage. The product of Team A's offensive rating and Team B's defensive rating estimates the number of goals Team A will score on Team B. CHODR was developed by Robin Lock at St. Lawrence University. (See also http://it.stlawu.edu/~chodr/.)

CCHP is similar to CHODR, but is uses an additive model instead of CHODR's multiplicative model. CCHP was developed by Eric Carlson at the University of Alaska-Fairbanks. (See also http://www.uafhockey.com/hexplain.html.)