Stat Man's Christmas Awards

Alright, the selections are in, and it's time to announce the winners!

Best Freshmen Men's Team:
Crash Test Brummies!
  Formed just in time for the MERDC tournament, it took them about 2 months to get their first win.  Nonetheless, they're now ranked #44 in the UK & Ireland, so they're the best new men's team.

Best Freshmen Women's Team:
Hull's Angels Roller Dames!
  Ranked one place above the Brummies, HARD's loss to Newcastle [B] helped to boost them up the standings to win this award.

Most Improved Men's Team:
Tyne & Fear!
  Tyne & Fear spent most of the season in the 40s, dropping as low as #50.  Then, their excellent performance at MERDC raised them 28 places to UK & Ireland #22.

Most Improved Women's Team:
Middlesbrough Milk Rollers!
  MMR started the year in the upper 30s, and are now knocking on the door of the top-10.  At USA-England, someone held up a sign "MMR are coming."  They weren't kidding!


Congrats to all the winners, you've clearly had a great season!

± and beyond

I just had to give it a great title, to see what happens when a computer tries to alphabetize that character.


Right now, individual skater stats usually end with the ±, or plus minus.  That's number of points scored by that skater's team whilst she was on the track, less number of points scored by the other team whilst she was on the track.

• Advantages
• Easy to understand: a skater with a positive helped her team win, a skater with a zero just broke even.
• Easy to calculate: for-against, could be done without computer assistance.
• Disadvantages
• Hard to calculate with: ± is centred on 0, and 0 is very difficult to factor in to future calculations.
• Boundless: there is no minimum value or maximum value.  Theoretically, a blow-out win could be orchestrated by 1 jammer, who's ± would be something like +80.

In my opinion, those advantages make the ± a great thing for coaches and individual skaters, on a bout-to-bout basis.  However, it's not as easy for derby journalists, statisticians, and fans of the game.


For those groups, there is another option: the jamming/blocking average.  This is the percentage of points that were scored whilst the skater was on the track, that were scored for that skater's team.  Thus, if the jam score was 4 to 1, the lead jammer's jamming average would be .800 and the other jammer's would be .200.

• Advantages
• Easy to use for calculations: it's centred at .5, so a 0 is exceedingly rare and refers to 0 impact on the bout.
• Bounded: all skaters will have a value between 0 and 1.  There is no possible greater or lesser value.
• Easy to understand: we're used to percentages by now.  A jammer has .525, she just slightly won.  .725, and she's got good control.  Easy!
• Disadvantage
• Difficult to calculate: this one requires a computer to come up with.

I think it's a much better option for fans, journalists, and statisticians.  It gives you, at a glance, how much a jammer or blocker affected the scoreboard in her favour.  As well, it can be compared more easily between bouts and skaters.


There is, as well, a third option.  The first two are concerned with every point scored.  What if we instead looked at benchmarks?  (Thanks to The Mighty Bush for help on this one.)

1. A jammer's job is 1st to get lead jam.  Thus, let's look at the percentage of jams where a jammer got lead.
2. A lead jammer's job is to record a full pass, denying her opponent any points.  Thus, let's look at the percent of lead jams where the lead jammer scored at least 4 points more than her opponent.
3. A non-lead jammer's job is to deny a full pass to her opponent.  Thus, let's look at the percent of non-lead jams where the lead jammer scored less than 4 net points.

• Advantages
• Easily to understand: this battery of three stats tell right away how successful a jammer is at those three aspects of the game.
• Bounded and easy for calculations: centred at .5, bounded between 0 and 1, so easy to apply further.
• Disadvantage
• Difficult to calculate: this one definitely requires a computer to calculate all the "if...then..." portions.

This option is great for coaches and skaters, as it gives simple yet detailed feedback on three vital aspects of the game.  As well, it's great for journalists, statisticians, and fans as it breaks down a bout and can give a great "why" for a team's success/failure.

So, there are a few good options to measure jammers.  How to measure blockers?  Maybe later I'll argue for why I like to use the exact same metrics to measure their performance.  What do people think?

Women's UK derby chart, 23-Sept-12

The rankings presented here are in accordance with the rules and consider Rollin News as the authoritative source for bout scores concerning UK & Ireland teams.  If a score is not listed as open or public on that source, it will not be included in this ranking.

How it works [with as little maths as possible]

Alright, you likely saw the Women's UK & Ireland Derby Chart on the other page.  I hope it makes sense.  If you think your team's rank is in error, or I have used the team's name rather than the league's, send me an email at Roush.adam.h@gmail.com and I'll sort it for you.  Just check on this page first to make sure any bouts which may have been missed are considerable.  Thanks!

Also, I will publish a second explanation with full maths soon.  Stay tuned if you love linear algebra!

Women's UK derby chart, 17-Sept-2012

In the weekly chart that follows:

• Only bouts with public scores between rankable teams within the last 12 months are counted for this chart.  As mentioned before, every other sport's ranking scheme has an expiry date for results, and it's time for derby to have the same.
• Only teams from regular bouting UK and Ireland leagues are eligible for ranking.  Due to the sheer number of leagues, I had to exclude continental Europe from the chart.
• A team with fewer than 2 rankable bouts is excluded from the chart.  As well, a team that has only played bouts against unrankable teams is excluded from the chart.  Both are due to the need for viable data.
• Arrows represent change from the previous week's ranking.  ⇏ indicates a previously unrankable team's début on the chart.  For the sake of this, I ran the rankings for the 10th of September as well.

National Rankings, quantitatively

So, if you haven't figured out by now, I like quantitative analysis.  Therefore, I was quite chuffed to read a paper by Dr. James Keener^[link], provided by Mr. Skipsey^[link], describing a way of quantitatively analysing the relative ranking of teams.

Now, there are several great systems in this world of ours, but most rely on teams all playing each other.  Derby doesn't do that.  Derby teams play who they want, and rely on subjectivity to guess who's better than whom.  That's where Dr. Keener's paper comes in handy.

England v USA stats

So, let's take a look at some numbers, shall we?

Team		Score	LJs	LJ ppj	PJs	PJ ppj	Short PJs	Stops	1Pass
3	England	70	7	5.7	4	11.0	1	7	14
1	USA	296	32	9.2	5	15.6	0	31	4

About the bout: 

USA of course outscoring England and winning the battle for Lead Jam status.  With lead jam, USA doing a little over 50% better than England.  Interesting to note here is that both teams were recording 2-pass derby with lead jam status.  The defence-offence transition was apparently a bit weak for both teams.

Both teams had a handful of power jams, but USA was better able to make use of them.  I, personally, attribute that more to the difference in the pack than that of the jammers.  The USA blockers were quite adept at getting a shoulder or a hip in the way, and then never breaking that contact.

Often the USA power jam defence was based on only one or two blockers engaging the jammer--the others simply made sure those two stayed in play.  The two who were engaging were often grabbing the far sides of each others' bodies, to make sure that wall stayed tight.  The amazing thing was that this was only done on the side opposite the jammer.  When the jammer tried to go through there, all the grabbing ceased, so that a devastating muliplayer block major was avoided!

USA able to keep England from scoring almost every time they had lead, but the Roses (it just felt right to call 'em that at the bout) able to prevent USA from scoring every lead jam.

One deciding factor was that Team USA were able to hold Team England scoreless the first 11 jams of the second half.  The lead was only 71 points coming back from the break, so that  jump provided the proverbial icing on the cake.

And the world? 

Team England showed their world-class power last night.  Canada were beaten by USA in the world cup 336-33, so the Roses out-performed the World Cup silver medallist side.  Canada recorded 9 LJs to USA's 25 in that bout, but that's within the margin of error of England's 7 LJs.

The USA showed their strength against the Scandinavians on Saturday, and defeated Finland on their home soil by a massive margin.  The tourists here did not bring their B-list skaters, they came to roll over the opposition wherever they went.

Nonetheless, little old England, that plucky little island country that has consistently punched above its weight this summer in Stratford, did so again in Newham.  The Roses taught the Americans that derby over on this side of the pond is not to be underestimated.

--[Edit: I am aware that Team GB is not equivalent to Team England.  However, English athletes were part of the team that punched above their weight in the Olympics, so I took a bit of artistic license.  I did have to take a moment in the broadcast to explain the nature of the UK as a union of countries to the US viewers.]--

Therefore, I think England should be considered the world #2 nation for roller derby.

What do you think?  Take a moment to fill out a simple poll and tell me where you think England, USA, Canada, etc. stand in the world of International Roller Derby. http://www.surveymonkey.com/s/YNXJV5H


Roll on Roses!