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Fun example of an observational study: Effect of crowd noise on home-field advantage in sports

Kevin Quealy and Ben Shpigel offer “Four Reasons the N.F.L. Shattered Its Scoring Record in 2020”:

No. 1: No fans meant (essentially) no home-field advantage

With fans either barred or permitted at diminished numbers because of public-health concerns, the normal in-game din dropped to a murmur or — at some stadiums — to a near silence. That functionally eliminated any edge that a packed stadium full of screaming fans might provide to a home team. That gap has been steadily closing over the years, but visiting teams never scored more, on average, than they did in 2020.

No. 2: Referees called fewer offensive penalties

A significant force driving the scoring eruption didn’t even involve players. On-field officials, adjusting the standard by which they enforced penalties, called the fewest offensive holding penalties since at least 1998. . . . On the other side of the ball, penalties for defensive pass interference increased for the third consecutive season, to its highest levels since at least 1998, which also extended possessions.

No. 3: Coaches Were Smarter on Fourth Down

At the same time, if teams weren’t successful on third down, more of them recognized the value of going for it on fourth down. Teams went for it 658 times, up from 595 last season, especially on 4th-and-1 . . . Instead of being aggressive solely in the second half, when score and clock decay might dictate it, teams went for it before halftime more than 200 times, significantly more than they did in previous years.

No. 4: The N.F.L.’s quarterback evolution accelerated existing trends

At a position long defined by pocket proficiency, the best of this next generation marries cherished passing attributes — accuracy, arm strength and downfield vision — with mobility, elusiveness and an aptitude for extending plays. . . . Unlike defensive players, who couldn’t simulate tackling drills as they trained away from their teams’ shuttered facilities, many quarterbacks improvised by gathering running backs and receivers— and even some linemen — in parks or at school practice fields to master the scheme and build chemistry.

This is great stuff. A few years ago I complained about a bad sports analysis from Quealy, so I’m really happy to see this new piece, which is thoughtful without being gimmicky.

A research question

There are lots of things above that could be studied further. Here I want to focus on Quealy and Shpigel’s first point, “No fans meant (essentially) no home-field advantage.” They continue:

“You don’t have to worry about the noise levels,” Steelers linebacker Avery Williamson said in an interview in October, when he played for the Jets. “You don’t realize how quiet it actually is on the field when you get out there. You could hear coaches talking across the field. It’s super weird.”

The subdued atmosphere created a more forgiving atmosphere for road teams, reducing the need for quarterbacks to use silent counts and allowing masters of the hard count, like Rodgers, to use his voice to draw opponents offside. Offensive linemen, in turn, could hear the calls more quickly and clearly. False starts dropped to a record low in 2020.

So here’s my question.

How can we study the effects of crowd noise on home-field advantage? The above point no. 1 is a before-after study, which could be thought of as an observational study with two data points, comparing NFL in 2020 to NFL in previous years.

There are various ways to expand the analysis:

1. Within games, focus on particular game situations where crowd noise would be expected to be more of a big deal.

2. Within the NFL, look at interaction with crowd size or crowd noise: if the above story is true, you’d expect to see larger home-team / visiting-team spreads in noisier stadiums.

3. Look at other sports.

There are probably some other ideas I haven’t thought of.

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