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My fantasy team uses a playoff system that Bill Simmons suggested a few years ago. In order to study it, I'd like to run Monte Carlo simulations of last year's post-season. To do so, I need to be able to compute the win probability for a pair of teams given the site of the game. Note this is not a prediction against the spread, just the orders of one team winning. This format also means that I can't use Vegas's point spreads, money lines, etc. because I need to be able to make predictions for pairs of teams that didn't meet in real life.

I thought that it would be easy to find a suitable model online, but I haven't been able to. Here's what I've tried:

  1. AdvancedNFLStats: In principle they supply all the needed information but I've been unable to reproduce their results. You can see a long post from me at the end of the week 7 team efficiency page that has gotten no replies. I would love to be able to get this model working.
  2. NFL Predictions uses stats from AdvancedNFLStats to run Monte Carlo paths through the post-season in some way that's slightly different from what AdvancedNFLStats does, but I can't find any info on the methodology.
  3. Simple Ranking System a.k.a. simple rating system: is focused on predicting margin of victory, not probability. More info here. The creator gives a formula for computing win probabilities here, but it's not clear to me that the same constants can still be used.
  4. Jeff Sagarin's ELO ratings: also aimed at point spreads, not probabilities

This page seemed promising at first but I didn't get anywhere following up on all the links.

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up vote 1 down vote accepted

The comments section on this page from Advanced NFL stats describes how to convert that website's weekly GWP values into win probabilities. A commenter named James writes:

The equation is: (H*(1-A)*F) / (H*(1-A)*F+(1-H)*A*(1-F))

Where H is the GWP of the home team, A the GWP of the away team, and F the home field advantage constant of 0.575.

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