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Saturday, July 26, 2008

Home Field Advantage - Stage 2

New home field advantage post

Your aren’t going to like this.

I don’t like this and I wrote it. In my mind, it attacks the very foundation of the game I love so much. But I’m filled with a sense of academic integrity to report on my findings, even if I don’t like my findings. So bear with me and read with an open mind.

Home field advantage is very real. We can all agree on that. The professional athletes in professional sports, the older, hardened men and women of athletics, are influenced by the venue in which they play. In college football, with huge stadiums looming over young kids playing an emotional game, the effect is magnified. This, for the college football fan, is what college football is all about. This is why 75% of the ACC sucks.

But what creates home field advantage? The screaming fan likes to believe that his perturbation of air molecules, along with the butterfly in China, prevented an opponent’s audible on third and long or inspired the corner to make that extra effort and break up the pass. Or maybe his prayer was so heartfelt and sincere that God couldn’t resist interceding on his behalf.

Those with experience in the game also have felt the affect of riding long hours on a bus or plane and dressing in a pink locker room, just a little dehydrated, just a little tighter than usual, just a little distracted by an unfamiliar environment.

One goal of mine since establishing this blog was to quantify home field advantage. Early on, I found consistently that home field advantage across the country in college football was worth about 3 to 3.5 points. But how does that vary by team?

When I started, I was hoping to produce a list like this one offered up by a wizened reader:

1. LSU
2. Florida
3. Tennessee
4. Oregon
5. Ohio State
6. Penn State
7: Auburn
8. Washington
9. Clemson
10. Wisconsin

With a few minor changes to match my own biases (e.g. my personal opinion of ACC football). But I had to do this statistically, objectively, and reproducibly.

For my purposes here, home field advantage is defined as the opponent adjusted differential between home and road performance. A good home field environment can also work in other ways—it aids recruiting, it inspires future and current boosters to open their check books, it fills the athletes with a sense of pride and respect for their program that improves the work in practices, etc—but I’m not concerning myself with these for now. This analysis looks exclusively at the difference between how a team performs at home and how it performs on the road.

With that in mind, I think it is also important to establish that an “advantage” in college football that doesn’t show up on the scoreboard is not really an advantage. Sure, it might be fun to hold out your arms and slap them together like a giant reptile with 75,000 other people, but if it doesn’t show up on the scoreboard its just entertainment, it's not an advantage.

Using all games since 1987 as my sample, after controlling for the strength of the team and its competition and removing teams with an insufficient representation, I found that almost every team in the country has experienced a home field advantage (with the notable exception of Navy which apparently plays better in the more liberal environments outside of Annapolis).

The teams on the list above do not fare well. Tigers in cages, stadiums that seat small metropolises, and a thousand combined years of tradition aside, LSU comes in behind La-La and Louisiana Tech, Ohio State behind Ohio and Kent State, and Penn State eeks out an extra .2 points at home than Pitt in their oversized, undermanned condiment stadium.

Instead, coming in at number 1, and with little doubt, are the Rainbow Warriors. The distance a team must travel to play Hawaii (and Hawaii must, in turn, cover to play anyone else) seems to be the most important home field advantage in college football-because it definitely it's not the intimidating environment of Aloha Stadium.

After that, the list seems rather random. Blue fields are apparently difficult to adjust to. And instead of Oregon cracking the top 10, Oregon State takes a proud spot at number 3.

These results disturbed me, so I went in search of an explanation. I tried to looking at conference games (and all games in weeks 5-12 for independents) in an effort to control the sample bit, but the list looks similar-- still dominated by the WAC.

I next thought that I might find something in close games (final point margin was 7 or less), where the crowd has the most effect. Instead, I found that home field advantage almost disappears completely. This, I thought, was the most condemning evidence of them all.

(Click to see a larger version)

For completeness, I've also included 95% confidence intervals. This means that you can be 95% confident that the real value of the team's home field advantage lies somewhere in that range.

My first, second, third, … , and tenth reactions to all these results were that there must be something wrong with my analysis, something wrong with the data, something wrong with my computer, my statistical package, the interaction of electrons on the atomic level or the universe as a whole. NO WAY does No. Illinois get more of an advantage at home than every team in the country with a stadium that seats more than 80,000. I’ve been at those games, and yelled for my team and I know in the depth of my soul that I had an impact—but apparently I, we, were just a little delusional. The reason my team wins at home is because the opposing team had to eat something different for their pregame meal, left their lucky socks at home, spent too many hours commuting and then couldn’t find the restrooms once they arrived.

But go and yell your heads off anyways, pace in the living room, curse, swear, pray, and curse some more and refuse to change your underwear if you think it helps. That’s the Atlas of college football.

P.S. I have two more ideas that will take me a little longer to apply but may interest the engaged fan. I'm going to control for the field surface and the distance traveled to see what results that gives me, but it will take me a little while to organize all the data and design the analysis, but stay tuned.

5 comments:

  1. Scott, once again your calculations and concept are fascinating. Your posts never fail to make me think, and rethink, teams. And in this case, stadiums.

    However, the one thing statistical analysis in sports cannot measure and factor is human emotion. The unmistakable feeling one gets when he/she enters into an environment that produces fear and/or intimidation. There isn't a number - a figure - you can attach to the way a group of young men's minds and bodies will react when it's time to leave the locker room and make the walk.

    As a former athlete, I can feel it just sitting here thinking back on certain games in certain basketball arenas.

    Take one good team. Not great, not poor. Let's say North Carolina State. First, send them to Hawaii to play. Upon their return, query the players about the travel, the meals, the field surface...you name it.

    Now, send them to Baton Rouge for a Saturday night game against LSU. Ask the players the same set of questions. I can practically guarantee their responses to you will be on the order of awe when discussing the difficulty in playing at LSU, and it has nothing to do with the guys they're lining up against.

    Forget the fact Hawaii is no match for LSU on the field (or, at the very least, on paper). Home Field Advantage still, after all the travel, meals and sleeping in different beds, comes down to that moment...that singular moment you walk out of the tunnel.

    I have always maintained on the radio that a great home field advantage won't win a game for a team. But might it tip the balance either in a crucial situation or even before the opening kickoff? I think so.

    I also contend, based on nothing more than personal experience in the stadiums, talking with players and standing at field level being able to practically feel the collective pulse of a team, that home field advantage may have a greater effect on the way the two teams play early in a game rather than in the second half. In so many places I've been at, games were either won, or nearly put away early because of the explosion of emotion, noise and adrenaline that nearly lifts you off the ground.

    I don't dispute that every team has a certain level of home field advantage. Of course they do. But when you listen to what the players say, they paint a picture that speaks volumes about what they face inside the stadium rather than what they've had to deal with outside of it.

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  2. Just a question about your analysis. In controlling for a team's performance at home, you had only one option: the team's road games. So I assume that the control sample was the team's road games (ignoring games at neutral sites, since they are rare). My question is: couldn't we, then, interpret this list as badness on the road, as well as goodness at home? Hawaii, for example, based on the distance they must travel, is notoriously bad on the road.

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  3. Anonymous,
    Technically, the value for HFA represents the difference between a teams performance at home and "not at home" where "not at home" includes games at neutral sites and true road games (with the opponents HFA statistically removed). So, as you say, we could interpret this as badness not at home, because it is completely impossible, statistically or otherwise, to differentiate badness not at home and goodness at home. The one statement is made relative to the other (they are bad on the road because they are better at home, and vice-versa). As you note, not everyone's "not at home" is the same--Hawaii's not at home is very different from Ole Miss's not at home. One reason is that Hawaii has to travel much further than Ole Miss for their road games, and I'm fiddling with distance to adjust for that (when you take distance into account, HFA shrinks to about 2 points on average). Other reasons include travel accommodations, weather, how well fans travel, etc. and I will not be able to adjust for these differences.
    Thanks for the comment

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  4. Scott, your example with ark state having a differential of 19 points. and then subtract 12.4 points. but would you not divide 19 by 2 to begin with as Home helps as road games hurt. i.e assume all things/teams are equal and everyone has a 3 pt hfa. they would win their home games by an average of 3 points and lose by three points, which is a difference of 6, not 3.
    or am I missing something?
    thanks
    John

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  5. Johnny,
    Very good question, and looking back on it, I realize it might be a little misleading in the post. Here's the actual calculation in the case of Arkansas State: They did 19.24 points better at home than on the road. Their home opponents were 12.4 points stronger, but that is not taking home field advantage into account for these teams. If we assume that these teams were 7 points better at home than on the road, the real SOS difference would be 12.4-7=5.4. So we subtract 19.24-5.4 and divide by 2 and we get approximately 6.85. The HFA(PD) values above are more precise, because I use the real HFA value for each team instead of this approximate 7 point value, but the principle is the same. Does that answer your question?

    Scott

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