November 20, 2009

Properly Evaluating Decisions

Commentators of all types have spent the week calling shenanigans on Bill Belichick for his decision to go for it on 4th and 2 from his own 28. The SG finally weighed in today. To put it mildly, he was not a fan of the decision.

The gist of the Simmons column is this- Stats are fine, but you have to use your eyes. Watch the game! And when the two don’t match up, the stats can't be trusted. I don't really fault Simmons for saying this sort of thing. It's how most people think. Here's an example of his thought process:

“In the biggest game of the regular season, when a football coach tries something that -- and this is coming from someone who watches 12 hours of football every Sunday dating back to elementary school -- I cannot remember another team doing on the road in the last three minutes of a close game, that's not ‘gutsy.’ It's not a ‘gamble.’ It's not ‘believing we can get that two yards.’ It's not ‘revolutionary.’ It's not ‘statistically smart.’ It's reckless. It's something that should happen only in video games, and only when you and your roommate are both high.”

I happen to think that’s a poorly reasoned paragraph. But I would bet that Bill Belichick wants every single coach and player the Pats play to think in that same way. He’s a great coach precisely because Belichick isn’t afraid to take the heat. Remember when he called for an intentional safety? I bet that if they had lost that game, he’d be getting the same reaction as he is now. That time it worked, and he’s a genius. This time it didn’t, and he’s a complete moron. But none of that matters to him. All he cares about is winning. Joe Posnanski made this point better than I ever could. The reason he wants people to think like Simmons is that he can exploit it and put to his advantage. He knows that decisions cannot be evaluated by the result, only by the expected result at the time the decision was made.

The problem with the anti-Belichick arguments is that they're on the fact that the attempt failed. Had the attempt succeeded, Belichick would be hailed yet again as a genius. Decisions, even in sports, have to be evaluated based on the circumstances the decision maker faced at that moment in time. Belichick knew that going for it gave the Patriots the best chance of winning.

(If you want to bring in the non-probability factors, he had, as recently as the 2006 playoffs, lost a late lead to the Colts by giving Peyton Manning a chance to win the game. In this game, the Colts were rallying and the Pats D was worn down. Lastly, the “not trusting the defense” argument fails because it’s equally arguable that he was saying- “look, defense, we’re going to go for it because it maximizes our chance to win, but if it fails it’s all up to you guys.” But none if this is the point.)

The point is that it was the right decision at the time, and Belichick was not afraid to make it. Most coaches wouldn't have the balls (see below).

Pats fans should be thankful to have a coach like that at the helm.

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It could be the case that the Sports Guy (and those like him) just don't understand probabilities. Look at the analogy he chose-

'But by Monday night, based on various columns and message boards (as well as e-mails to my reader mailbox), you would have thought Belichick was a genius for blowing the game. He played the percentages! It wasn't as crazy as it looked! By this logic, Belichick also should have held a loaded pistol to his head on the sideline, spun the chamber and tried to shoot himself like Chris Walken in "The Deer Hunter." If those 1-in-6 odds came through and he succeeded, we could have said, "Hey, he played the percentages: 83.6666 percent of the time, you don't die in that situation! You can't blame him for what happened!'

The analogy fails horribly because “the percentages” in the Deer Hunter case are-

Choice 1- Walken doesn’t put the gun to his head. Chance of dying- 0%.

Choice 2- Walken puts the gun to his head. Chance of dying- 16.67%.

It’s obvious which choice is “playing the percentages.” (Also, does the SG have editors? 5/6 is 83.33%.)

In Belichick’s case

Go for it- Win Probability: 79%

Punt- Win Probability: 70%.

(Numbers taken from Advanced NFL Stats.
)

Going for it is playing the percentages.
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(further reading- Stevin Levitt @ Freaknomics. Coaches and the principle-agent problem. TMQ makes this point often, too.)

c/p @ http://madisonthree.blogspot.com/

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