This thread is addressed to anyone who has organised or participated in a VRC league.

Here is the document that describes how leagues should be run:

League Play 2013-2014

The document says that teams are to be ranked by win%, and that teams must compete in 75% of the available matches in order to be considered for the finals.

Win% ranking is not ideal in a competition where different teams play different numbers of matches. For one thing, teams who play fewer matches will have greater variance in outcomes. More importantly though, teams are advantaged by choosing not to compete if after playing the minimum number of matches they have a higher than expected win%. These teams could choose to compete under a different number, but not every team has that option and some might choose to miss events if they think that competing might drag them down in the rankings (potentially pulling them below the threshold that would qualify them for regionals/states/nationals). Having teams sit out because of a quirk in the ranking system is clearly not good for the competition.

My question to you is: does this happen? Are you aware of any teams who have chosen not to compete at the end of the season because they were worried their ranking might slip? And if this hasn’t been an issue in your competitions with the minimum number of matches at 75%, how much of an issue do you think it would be if that limit were 50%? or 25%?

There are ways of ranking teams that would make this less of an issue. One way is described here and is based on compensating for the greater uncertainty associated with teams who have played fewer matches:

http://www.evanmiller.org/how-not-to-sort-by-average-rating.html

This rewards teams who have maintained the same win% over more matches, because it’s more likely that their score accurately represents their ability. By changing the confidence parameter you change the relative importance of matches played and win%.

You can’t change the fact that teams whose current rating is higher than their expected full season rating are advantaged by dropping out. What you can do is change the way those ratings are calculated so that more matches played increases the expected rating, making that situation less likely.

Since VRC in New Zealand has become too big for every team who wants to to attend Nationals, Kiwibots is planning to begin running a league in each region to decide which teams qualify.

Kiwibots have tentatively scheduled 12 ranking scrimmages in Auckland between June this year and February next year. Since scrimmages in Auckland are frequent, the number of teams at an average scrimmage has historically been less than 75% of the number of available spots allocated to Auckland at Nationals. This will mean that the required number of matches played in order to be ranked may have to be reduced from 75% of the maximum to something lower. This would increase the probability of teams completing their minimum number of matches with much higher than expected win% scores, which is why I’m asking what your experience has been with what these teams choose to do in that situation.