When is a conversion worth the risk?

With 12 minutes left in Super Bowl XXXVIII, coach John Fox had his Carolina Panthers attempted a two-point conversion after drawing within five points of the New England Patriots. The conversion failed. When the Panthers scored another touchdown, they again tried for a two-point conversion -- and again failed. The Patriots then scored their own touchdown and successfully pulled off a two-point conversion to take a seven-point lead.

Many armchair quarterbacks decried Fox's decision to go for that first two-point conversion with 12 minutes still left in the game, especially since the Panthers ultimately lost in the last seconds on a Patriots field goal.

The critics argued that if the Panthers had just kicked that first extra point, there would've been no failed second attempt at a two-point play later in the game, and New England wouldn't have made their own two-point play in the fourth quarter. In that case, Patriots kicker Adam Vinatieri's field goal with four seconds left would've tied the score at 31-31, rather than winning it 32-29.

The critics had data to back them up: Two-point conversions succeed only about 40 percent of the time, while kicking the extra point is successful 99 percent of the time. With so much time left for the game to unfold, why did Fox take such a risky move?

At least one statistical study on two-point conversions would conclude that Fox made the right decision.

Rutgers professor Harold Sackrowitz, used probabilities to determine the best strategy -- go for two or just kick the extra point -- for 532 different game situations, based on the difference in the score and the time remaining in the game.

Sackrowitz's table indicates that John Fox did the right thing by going for two when his team trailed by five points with 12 minutes left. In fact, if your team is trailing by five points and it's late in the -- second quarter -- it's still to your advantage to go for two. The thinking is this: If the two-point conversion is successful, you'd still be tied if the other team scores a touchdown and kicks an extra point. If it fails, then even a touchdown and two-point conversion by the opposing team would give it only a three-point lead -- which could be erased if your team gets the ball back and kicks a field goal.

Statistically, Fox made the right move. But with just a 40 percent success rate for two-point conversions, Fox was still faced with the fact that his decision was more likely to fail than to succeed.

Sackrowitz's research turned up some other interesting extra-point quandaries. Say that your team is ahead by two points with about 10 minutes left in the game -- time enough for each team to get two more possessions. Makes perfect sense to go for the easy extra point and take a three-point lead, right? Wrong. Your team would be better off if it went for the two-point conversion and the four-point lead. Why? If you succeed, you're assured of victory if the other team can only muster a field goal over their next two possessions. But if you fail and the other team manages to score a touchdown and extra point, then you trail by five and can still win with field goals in each of your last two possessions. There are just more ways for your team to win if they go for two rather than kick the extra point.

Of course, the strategy table isn't fool-proof. For instance, the strategy changes if you expect your opponent to get one more possession than you will over the remainder of the game. In that case, you should avoid the two-point play and just kick the extra point. In situations like this, the correct call for the coach all comes down to whether he can correctly predict whether his team will have the last chance to score before the clock hits zero.

Additionally, the table doesn't have much meaning in a blowout. Of course, that didn't stop Texas from going for two when the Longhorns were already up 51-3 in the third quarter of their 2005 game against Rice. Perhaps Texas coach Mack Brown didn't want to run the risk of over-matched Rice scoring seven straight touchdowns and sending the game to overtime at 52-52.

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