# Is ‘home field advantage’ worth taking down a banner for?

Do you think if you flipped a coin in a mint, it would show heads more than tails? Imagine if we set up a small coin-stadium in or adjacent to the mint where the coin was made, where other coins would sit around watching the coin get flipped. Say we flipped the coin outside of the stadium first a bunch of times and showed that it was relatively 50/50 whether it was going to be heads or tails, but then we went back to this mint-stadium and flipped the coin 3,879 times, and it turned up heads 2,219 times. With a simple statistical test, you can show that the probability of a 50/50 coin giving this result in the stadium is 0.000000000256%.

Football is not a coin. However every team – no matter how good or bad – plays 16 games in the regular season: 8 of those at their own stadium and 8 of those at an opponents stadium, so a good team will play at home as much as a bad team will. Yet when you run through the stats the ‘home field advantage’, i.e that the home team are more likely to win than the away team, is more statistically significant ($8\sigma$) than the detection of the Higgs boson ($5\sigma$).

What I’ve got: 14 years of regular season NFL data (2000-2014)  – a few thousand games, half a million plays.

What I’m going to do with it: Try and find which bits of a football game are affected by ‘home field advantage’ in a (fairly) rigorous manner.