NCDA moves to the Gonzalez System

CHICAGO – Office of the Director of Officiating (and Records): The NCDA Executive Board has voted to move to a new ranking system. This new system is closely based on the earlier “Gonzalez System” and the new Gonzalez System will replace a combination of four different systems, which was used in seeding the Tournament Bracket for Nationals 2014, 2015, and 2016. The vote concluded on 2016-10-24; the motion carried 3-1, with one abstention, plus Director of Nationals assent.

For the full detail of the Gonzalez System, see its Policy documentation. See below for a short and simple explanation of the system.

The system detailed here is the same Gonzalez system we’ve been using in the previews/standings posts over the last few months.

Overview

The Gonzalez System is a computer ranking model similar to Elo and is a rating exchange system based on research performed by World Rugby. It has been adapted by the NCDA to the demands of College Dodgeball, but can be tuned and customized endlessly to incorporate accurate data.

If the high seed has a rating of 50 and the low seed a rating of 45, the Ratings Gap between these two ratings is 5.

The Gonzalez Exchange will be .500 if the high seed wins, which we count as the predicted result. The teams trade points equal to the Gonzalez Exchange: the winner gains the exchange, and the loser gives up their points. If the low seed wins, the low seed gains 1.500 in a technical upset. The low seed gains more points for defeating a tougher opponent.

The Rating Exchange is a scale from 0 to 2 rating points. The exchange directly corresponds to a Ratings Gap of 0 to 10 rating points. There are two types of exchanges.
A predicted result will have an exchange from 0 to 1 rating points.
A technical upset will have an exchange from 1 to 2 rating points.

Short Formula: (1* ((1) * ((((45 + 0) – (47 + 3)) * 0.1) + 1))) = 0.500

There are only a few modifiers that currently effect the formula:

    • Home Court AdvantageAdd 3 points to the Team’s Rating for a match played in their home facility. If neither team possesses a home court advantage, the modifier will not be applied. [Edit: The HCA has since been set to 1, a more appropriate value]
    • OvertimeMultiply the exchange by 0.5. The rating exchange is calculated normally, then halved.
    • NationalsMultiply the end exchange by 2. This signifies the importance of the post season event, and any matches played during Nationals account for double the Ratings exchange. There are many reasons to support this: Nationals is played under better and fairer conditions. The Officials are better, more competent, more numerous, and are often neutral to either team playing.

Additionally, the biggest new change to Gonzalez system is that only a portion of a team’s rating is retained from Season to Season.

Teams keep 75% of their rating from the previous season. This matches the data reported by Member Teams in the Summer 2016 off-season Proposal vote. On average, teams retained about 75% of their roster. This causes a minor hit to predictability (about 1-2%), but better reflects real world “losses” on rosters between seasons. For the remaining portion of the rating, add 25% of the League Mean Rating at the end of the season is to the Team’s initial rating for the upcoming season.

Please comment or contact me personally if you have any questions regarding how the Gonzalez system works.

Author: Zigmister

DePaul Dodgeball #68 &
NCDA Director of Officiating

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