JPG recently asked me how I apply Elo ratings to American Football.
I find this easier than real football, for two reasons. One, the elimination of the draw as a possible outcome, and two, I use the ratings to directly determine a points differential between the two teams.
For example, today sees the New Orleans Saints at home to the Oakland Raiders. I have the Saints with a bonus for home advantage rated at 25 points, and the Raiders at 16. The handicap for this game has Saints -7.5 available at 2.16. To me this is value.
About Me
- Cassini
- I have had a life-long interest in sports and after studying Pure Mathematics with Statistics at secondary school, have been fascinated by odds and probability. The first system I came up with was a simple one - back the favourite and double up after a loss until a winner. Simple enough in theory, and I told my Dad about it. Not being a betting man himself, he ran it by some of his colleagues, and came home to tell me that it wouldn’t work because a long losing run would mean that the bank would be empty. Then there was always the possibility that the winner would be returned at odds-on, meaning that the total returns would not match the outlay. Not what a ten year old wants to hear! Only slightly daunted, I then went on a search for the Holy Grail, the secret to riches that I knew was out there somewhere. Finally in 2004 I stumbled across an article about Betting Exchanges and four years later I was able to make a steady profit.
Cassini, thanks for the info on this mate. Your quite right, once youve got your ratings into a points expectancy, its relatively a lot more straight forward to apply to betting markets then Soccer (mainly due to the draw.)
ReplyDeleteHowever, the problem Im having is the first part. Firstly, what adjustment do you use for home advantage? Traditional soccer odds compilers have used a weighting of 1.4 (or 40%) for the home team whilst ELO adds on 100 points to the home teams rating to calculate the win expectancy.
After this, how do you convert your win expectancy into a points scored expectancy? Unless you're using an ELO approach Im not aware of. I also dont know how to adjust a teams rating after a match relating to the size of their win or loss.
Any help on this would be greatly appreciated! - JPG
JPG - Home advantage is simply 3 points. Nothing sophisticated there. I think that with systems, it is often too easy to over complicate things. As for adjusting the ratings after each game, I use a unique sliding scale adjustment based on the margin of defeat / victory, and I don't count overtime. I can e-mail you the precise numbers I use if you would like, but you are probably just interested in the method and can throw your own numbers in as you see fit.
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