Data Crunch — Home Field Advantage?

Sorry for the delay!  I am told there are only two more football weekends, so by popular vote, we are going to stay chatting about football data through the remainder of the season.  Let’s do this.

After last weeks eye opening stats on how badly we (the Broncos and I) do not want to play in Foxborough, (we may or may not have started using derivatives of “Fox” in our family vernacular to indicate a place you don’t want to go), we wanted to look and see if other teams struggled on the road.  Is home field advantage a real thing?

To look at the question, we used all the games from the 2013 NFL season (256 games). As a simple start, we wanted to look at the number of home wins vs. visitor wins, because if the home team won only 50% of the time, then this would be easy to prove.

Home Team Performance

katiepie

This turns out to not be the case.  The home team won nearly 60% of the games, which has a P-value of .0018 (p-value is the probability of something happening by chance if the factor you are studying actually does not affect the outcome — making this extremely unlikely to happen by random chance)
Next we drilled down to see if, for the 2013 season, it just so happen that the best teams played against the worst teams on the road — for example the Denver Broncos (13-3) playing against the woeful Houston Texans (2-14).  To examine this we looked at each team to see how many home wins they had vs road wins.  If home field advantage is a myth, then bad teams would lose equally at home, or on the road, and vis versa for good teams.
This ratio of home wins to road wins is shown below.
SGPlot12
This plot show the ratio of home wins to road wins for each team. The ratio would be 1 if home field advantage doesn’t exist — you would expect teams to have as many wins on the road as they did at home i.e. 4 wins at home:4 wins on the road = 1.  The higher the ratio number, the more games were won at home as on the road.   If their ratio is 2, they won twice as many games at home as they did on the road. i.e. 6 wins at home:3 wins on the road = 2. You can see most teams performed better at home.
It appears as though the teams with the highest ratios seem to be those teams in the bottom third of league like the Vikings (6-10) with 5 home wins or the NY Jets (8-8) with 6 home wins.  It is also interesting to note the teams who perform worse at home, Jacksonville, Philadelphia, and Tennessee.  What do you think that is?
For more gory details, click below!
We also wanted to compare teams that played each other twice during the regular season.  Within each division, teams play each other twice — once at each city.  This accounts for 96 of the 256 games in the regular season.  We looked at the Total Yards, Turnovers, and Points.  The results showed no real difference in turnovers, a surprising result of home teams gaining less yards, but the in the only metric that really matters, points, the home team scored on average 3.2 more points than the visiting team.
(the vertical lines above each teams’ name represent the span of the differences between that team’s performance at home, and then on the road against the same team. For example, in one of their inter-league games, the Cardinals scored 20 more points at home against that team, versus when they played them on the road.  In another inter-league game however, they scored 7 points less at home, than they had on the road, against that same team.  All other inter league play fell in-between those two points.)
Take a peek

SGPlot16   

SGPlot15
SGPlot17
Lots to consider.
So — for mediocre teams, playing at home really seems to help.  Why do you think some stadiums give a better advantage (and did you see how many times Manning drew the defensive line offsides Sunday!!!!  Let’s talk about that, too.)
Data sourced from nfl.com.  Big thanks to Jared running the stats, making the graphics and writing up many of the explanations. Except, the pie graph.  I made that, and am pretty dang excited about it.
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One thought on “Data Crunch — Home Field Advantage?

  1. Jared January 13, 2014 at 10:49 PM Reply

    Watching Payton lure Chargers offside was reminiscent of the other great Broncos QB back in the day http://youtu.be/yM1HZu_9Naw.

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