The Two Point Conversion When Eight Down

[CanadaLowball]

my main concern about this whole thing is whether or not 42% actually represents the probability of success.

its not exactly rolling dice or dealing cards we're talking about, so are we able to apply past success/failure rates to current situations that may not involve the same plays and players and all the other factors.

so basically, what i'm asking is this: at any given time, does a team attempting a 2 point conversion really have a 42% probability of success?

[shemp]

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But the bigger problem with the coaches statement is that it was a RATIONALIZATION after the fact. If it was said by someone who understood the math and legitimately felt it should be rejected, fine. But this kind of thing is usually said by coaches AND ALL SORTS OF SUPPOSED EXEPERTS IN MYRIAD FIELDS to defend their stupidity. They didn't have any idea that theoretically the two point conversion or any of the myriad of mathematically based conclusions experts in other fields are unaware of, is the right decision. So they scramble to justify their ignorance.

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Consider another possibility: many reach decisions on some "instinctual" level that may be at least as accurate as the simple model you've constructed. They may not be aware of the math or be able to articulate their reason in a way to satisfy you, but their decision making is far better than you credit. Just a possibility.

I'd be interested to see the data more fully analyzed, something like dividing teams into quartiles by offensive strength and looking at success rates. And a similar analysis of defensive teams. Further, breaking it down on best running v. best passing offenses -- best running v. best passing defenses. I could think of a few more, but that would be a start.

[iggymcfly]

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The NCAA and the NFL have similar statistics for the success rate of two-point conversions and extra points. In the NFL the figures are 43% for the two-point conversion and 94% for the extra point, while in the NCAA the figures are 43.5% and 93.8% (Mallory & Nehlan, 2004). I’ll use the 43% and 94% figures for most examples in this paper, and will also develop the general formulas to show when the “go for two first” strategy is best. I’ll assume initially that the two sides have equal chances of winning the overtime, and will then extend the analysis to consider the more general case of what to do if, for example, the coaching staff believes that they have a higher or lower chance of winning in the overtime.

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I Googled "NFL, statistics, two-point conversions" and got the above from a site which was coincidentally supporting this exact same argument that Sklansky brought up. The reason that the XP% the other poster found is so much higher than this figure may be that it doesn't account for bad snaps or blocked attempts which would lower the overall percentage significantly.

I've wondered myself many times why coaches don't go for two in this situation, although I've always assumed that the 2-point conversion percentage was closer to 50% than it is. Still though, it seems like a trivially simple concept.

[sunspots]

What if a tie puts you in the playoffs or a rash of late 4th quarter injuries on the other team gives you better apparent odds in overtime.

I am a football official.... and I do think that a lot of coachs are logic challenged... I see them do very dum things all the time. But the very good ones can read situations and make adjustments in strategy very fast based on changing game factors.

[TimTimSalabim]

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think Yeti made a good point. A team who makes a comeback like this most likely has a greater win percentage than 50% when making it to OT. Id say this percentage (of course this percentage would always be an estimate the coach would have to make) would be big enough to swing the decision to a kick the majority of the time.

So maybe the decision to kick should be based on how the team fell behind in the first place, if they fell behind because of a few fluke plays, then go ahead and kick, but if they fell behind because they were getting their ass handed to them and then made some fluke plays and came back the decision should be to go for 2.

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Given no other information but that they are currently down by 14, it is much more likely that they are the weaker team. The fact that some small percentage of the time they will come back to score two touchdowns in regulation does not change that fact.

[Insp. Clue!So?]

I think the points you are missing include:

a) These sorts of situations occur frequently, and taken in aggregate would add significantly to win probabilities

b) they can be computed before hand, at little cost, and presented in an easily-understood way; the coach is free to accept or reject the info by combining it with everything else he knows/feels/whatever about the game (in fact he may even want to make mathematically break-even plays if their intrinsic factors' volatility makes them in fact the better move in a specific instance).

You could probably hire a staff game-optimizing geek for 50K/year. He might increase your per-game win prob. by 5 percent. What's an extra win/year worth to an NFL team? 10 mil? 20 mil?

[Magic_Man]

Just re-skimmed this thread because of the new post, 2+2 for 2. I didn't see anyone mention this, but maybe I missed it:

If all the teams start going for 2 in this spot, won't the percentage change drastically from 42%? I'm not sure if it will go up or down. It all depends on whether it is fundamentally easier to make a 2pt or defend it. Could 2+2 for 2 actually make the situation -EV?

~MagicMan

[PartySNGer]

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they kick the extra point when they should go for two

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Often this is also the other way around.

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One of these is a mistake (I think) I remember seeing twice. A team is down by 15. They score a touchdown (so they are now down by 9), and they go for the 2-pt conversion. They miss, and now they still need 2 scores. Isn't it *much* better here to kick the PAT and make it a 1 score game?

-Tom

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If you have to make a 2 point conversion why would it make any differnece if you attempt it with 4 min left, or with 10 secs left. In fact i would think that going for it on the first try is MUCH better since when you miss there might still be a way to get the ball back twice (go for two onsides kicks) and have a shot at planning the game better. If you miss on your last shot you have no way of altering your game plan to reflect that fact.

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Exactly, I see this all the time. Say the score is 28-12 with 8 minutes left and you score making it 28-19 so obviously you will need a 2 point conversion at some point. Why would you not go for it now? If you go for 2 and miss you know that you still need 2 scores so you can plan for this. If you go for a PAT and are down 8, the coach will play the rest of the game as if they are down 1 score and then if they miss the 2 with seconds left, they will lose the game. You will have to go for 2 either way, but doing it immediately makes so much more sense.

[NMcNasty]

Another thing I find interesting is that apparently all teams everywhere seem to think their 2 point conversion success rate is below 50%. Maybe this is true in the NFL, but surely there are lopsided college match-ups where a team would expect its success rate to be above 50%. If this were the case they should be going for 2 after almost every touchdown.

[mjkidd]

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Exactly, I see this all the time. Say the score is 28-12 with 8 minutes left and you score making it 28-19 so obviously you will need a 2 point conversion at some point. Why would you not go for it now? If you go for 2 and miss you know that you still need 2 scores so you can plan for this. If you go for a PAT and are down 8, the coach will play the rest of the game as if they are down 1 score and then if they miss the 2 with seconds left, they will lose the game. You will have to go for 2 either way, but doing it immediately makes so much more sense.

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With eight minutes left, a field goal and a touchdown is not unrealistic.