rockabilly

The Jammer Quotient

The JQ is a statistical comparison of jammers based on their rankings in five categories. The maximum JQ a jammer can receive is 50. The table below illustrates the evaluation of a JQ for the February 27th bout between ToRD’s CN Power and the Rideau Valley Vixens (only the top 5 are shown)*.

Jammer Total Points Points Per Jam Plus/ Minus Jam % Lead % JQ
Lunchbox (CNP) 48 (9) 4.36 (9) +36 (9) 23.4 (8) 72.7 (9) 44
Land Shark CNP) 53 (10) 3.78 (7) +45 (10) 29.7 (9) 57.1 (7) 43
Defecaitlin (CNP) 45 (8) 4.5 (10) +29 (8) 21.2 (6) 70 (8) 40
Marvel S. Maven (CNP) 25 (7) 4.16 (8) +20 (7) 12.7 (3) 100 (10) 35
Soul Rekker (RVV) 19 (6) 1.18 (4) -35 (5) 34 (10) 50 (6) 31

CN Power’s Lunchbox received the highest JQ. Interestingly, she didn’t actually lead in any of the five categories but placed second in four and third in the fifth (the numbers in brackets designate the ranking points, 10 for first place, etc). So for this bout, consistency was rewarded, as I imagine it always will be. Overall, all of the CN Power jammers had their way with the Vixens; despite a huge effort by Soul Rekker, the difference was in the jammers. The game was essentially over after the fourth jam when Defecaitlin (that’s Dust Bunny to all you Gore Gore fans) skated to a double grand slam and more than doubled the lead to 19-2.

This particular example doesn’t provide ideal data for a number of reasons. For one, it’s just one game, and there were only eight skaters who jammed a statically significant amount of times (I cut it off at 6 jams). The more data available, the more accurate the JQ, so during ToRD’s regular season, the teams will play enough games and get in enough jams to make a much more accurate judge of the statistical significance a jammer has to her team.

The data in this example are also skewed heavily in CN Power’s favour given the one-sided nature of the bout (199-49). I wouldn’t expect such high JQs over an extended period of time or among a much more even playing field. .

In the next post I’ll look at each category in more detail and justify the decision to include it.

* These stats are unofficial and are based on post bout analysis of video shot by Layer9.

Introducing The Derby Nerd

Lady Gagya makes some space for Land Shark.

Like any other sport, you need to watch a lot of roller derby to really understand it. But it doesn’t take too long for all of that violent frenzy to turn into something a lot more coherent. For me it happened in Montreal during a La Racaille game. I know that because I clearly remember the moment, seeing the extraordinary Iron Wench cutting her way through a pack, grabbing jerseys, accepting assists, dodging shoulders. It was at that moment when I realized that all of the chaos was actually quite orchestrated.

It’s been a few years now since a sudden surge of roller derby in Canada saw teams emerge in Toronto, Montreal, Hamilton, and other cities very soon after. We’ve gotten to the point now where the sport in Canada (at its very best) has developed to nearly the highest levels. It’s an exciting time to be a derby fan, and things just seem to keep looking up.

Almost as soon as I had my moment of derby clarity, my sports brain took over and I started to think of different ways to statistically compare the jammers. After a few false starts, I eventually developed something that I’ve been calling “The Jammer Quotient” or JQ. Its inspiration is varied, but basically it gives points to jammers based on their rankings in five different categories (total points, points per jam, plus/minus, jam %, and lead %). The top jammer in each category gets 10 points, the second 9, the third 8, etc (some fantasy sports players may recognize this points system). It might sound complicated, but it all adds up to one simple number between 10 and 50.

I’m working on a practice JQ comparison based on CN Power’s resounding 199-49 victory over the Rideau Valley Vixens on February 27th. A one game analysis isn’t ideal, especially a bout so one sided, but it’ll make for a good practice run.

I’ll post it shortly.