December 2012


Ok, this whole article is a kind of speculation on my part. DVOA is generally sold as a kind of generalization of the success rate concept, translated into a percentage above (or below) the norm. Components of DVOA include success rate, turnover adjustments, and scoring adjustments. For now, that’s enough to consider.

Adjusted yards per attempt, as we’ve shown, is derived from scoring models, in particular expected points models, and could be considered to be the linearization of a decidedly nonlinear EP curve. But if I wanted to, I could call AYA style stats the generalization of the yardage concept, one in which scoring and turnovers are all folded into a single number valued in terms of yards per attempt.

So, if I were to take AYA or its fancier cousin ANYA, and replace yards with success rate, and then refactor turnovers and scoring so that turnovers and scoring were scaled appropriately, I would end up with something like the “V” in DVOA. I could then add a SRS style defensive adjustment, and now I have “DV”. If I now calculate an average, and normalize all terms relative to my average, I’d end up with “Homemade DVOA”, wouldn’t I?

The point is, AYA or ANYA formulas are not really yardage stats, they are scoring stats whose units are in yards. So, if really, DVOA is ANYA in sheep’s clothing, where yardage has been replaced by success rate, with some after the fact defense adjustments and normalization from success rate “units”.. well, yes, then DVOA is a scoring stat, a kind of sophisticated and normalized “adjusted net success rate per attempt”.

Things that are easy to note: the teams with at least 9 wins are either guaranteed a playoff birth, or have, at worst, a 99% chance of making the playoffs. The teams with 8 wins have a very good chance of entering the playoffs. Those teams with 7 wins have at least a 50% chance of making the playoffs. Those with 6 wins have between a 5% to 30% chance of making the playoffs. Let’s say they are hoping to get in.

Data from week 12

2012_stats_week_12

Data from week 13

2012_stats_week_13

The methodology of these stats is discussed in previous posts in this series. If you’re wondering where I’m getting odds to go into the playoffs, see this post. If you’re wondering what chance your team has of winning in the playoffs, see this post on my logistic regression methods, based on studies of playoff games. How would your ranking in the playoffs affect your chances of getting into the Super Bowl? We studied that here.

I am not a proponent of the notion that regular season offensive stats are predictive in the post season. My studies suggest p on the order of 0.15 for offensive stats in the post season, and thus aren’t predictive enough for my tastes ( p <= 0.05). That hasn't stopped Football Outsiders from pretending that their proprietary stats are predictive and calculating playoff odds with their tools.

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