# Deferring the Coin Flip: Maybe It Is Not a Toss Up Decision

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A flip of the coin may be deciding games, but not in the way that you imagine. Jim Trotter at Sports Illustrated did a story on the choice of taking the ball first or deferring to the second half. The evidence suggests that coaches may want to consider deferring more often, so that they get more second half possessions.

Coaches seem to be divided on the topic of whether they want to get the ball first to start the game, or to defer to the second half, and then choose to start with the ball after halftime. Through last weekend’s games, coaches are opting to defer to the second half when winning the toss 51.3% of the time in 2012, and that is up from 41.8% of the time last year.

Is there justification for that increase? Trotter presents the numbers:

The difference of opinions could be traced to no direct correlation between the outcome of games and the decision on whether to receive the opening kickoff or defer. Since the start of the 2010 season, flip-winning clubs that have opted to receive first are 185-209 (.470), versus 140-115 (.549) for those deferring.

Often, we take small sample sizes in sports and draw big conclusions. Here, Trotter is being too conservative, though. Add those games up, and we have 649 events. The team starting the game with the ball after winning the toss has won 47% of the time. The team starting the game with the ball after the opponent won the toss but deferred has won 45.1% of the time (this assumes that no one chose to kick after an opponent deferred, and I don’t recall anyone doing that). Combined, teams starting with the ball at the beginning of the game have won 46.2% of games.

Now, if you had an actual coin that you were testing, and after 649 tests, heads was coming up only 46.2% of the time, you might have a problem with the coin. The p-value is 3%, meaning it is statistically significant at the 5% level, the most commonly accepted value for statistical significance.

There’s an actual reason to think that having the ball to start the second half is an advantage. It’s the same philosophy as to why a college team would prefer to have the ball last in overtime, on a much more diluted scale. You have a better idea of what you need in the second half, and will always have at least as many possessions as your opponent.

The team that starts each half with the ball will have either the same number, or one additional possession. In the first half, teams are more likely to waste this possession than in the second half. You get the ball with a minute left in the first half, in a close game, deep in your own territory? How aggressive are you? Maybe, but maybe not, and you just take a knee or run some plays to end the half before having to punt back.

In the second half, you know what you need more clearly, and act accordingly.

Of course, just because the results are statistically significant doesn’t mean that starting the second half is that big an advantage. Maybe the better teams, for reasons other than the coin flip and when they have the ball, happen to be starting in the second half more.

Bill Belichick, for example, has deferred every single time (33 of 33) he has had the option since opening day of 2008, when the rule change allowing deferrals was implemented to match the college rule. Perhaps he is superstitious after starting that game with the ball where Brady got injured. Perhaps he believes it is a strategic advantage, and Belichick will take any small advantage he can find.

Here are the teams who have always chosen to receive when winning the toss this year: Chargers, Chiefs, Jaguars, Lions, Saints and Texans. Those teams are a combined 22-33 this year, and for teams like the Jaguars and Chiefs, had they chosen the opposite, well, they weren’t going to change their fortunes.

Here are the teams who have always deferred in 2012: Bears, Bengals, Buccaneers, Cardinals, Patriots, Redskins and Seahawks. Those teams are a combined 35-29.

[photo via US Presswire]

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