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Comment by mdeck_ | Hacker News Reader

> Conclusion

> We can see that referees’ bias towards away sides has completely changed without an audience in stadiums.

> Previously, away sides used to get more yellow cards in all leagues, and they also had an inferior fouls to cards ratio. However, without an audience, the disparity has disappeared, and in fact, the trend has reversed in some leagues.

Um, where is the analysis explaining why these circumstances are concluded to be evidence of differential referee treatment of (identical) behavior by the soccer players rather than identical referee treatment of differential behavior by the soccer players? This seems like an enormous premise that—correct or not—is accepted without a moment’s consideration.

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Yeah away teams not under the emotional pressure of the crowds may keep their cool better and not cross the line into getting cards.

You'd need some objective way to determine if fouls deserved or didn't deserve a yellow card and be able to show that the same fouls were still being committed, but the refs were judging them differently.

Biggest problem is they don't have an explanation for the trend "reversing". If the hypothesis referee bias in front of home crowds is the main factor is correct, home and away card allocations should follow the same pattern within a small margin of error in the absence of crowds, not reversed with sometimes greater magnitude.

Most obvious reason for away teams committing more fouls per booking in an empty stadium is tactical: away teams are often set up to defend more, in a well structured manner, which means the ratio of inconsequential fouls vs cynical fouls to stop the counter attack, massive misjudgements and losses of temper is likely to be higher

This is compatible with the hypothesis that a 'biased' ref is less likely to let a side get away with regular inconsequential fouls when the fans are screaming at him. But it's also conceding the very large role played by tactical approaches which stats suggest have also changed since the pandemic

Absolutely.

I think the players are behaving differently. My thought is that the games will appear to be more similar to training ground practices where the opposition are your own teammates, so the sorts of tackles and behaviour the players express will be different as you don't want to risk injuring your own teammates.

Overall i think the quality of football played has improved without crowds although it's not the same experience without the fans.

That's always the case with study vs experiment. If you didn't control for all the variables but one, you can't make a conclusion about cause.

I think the honest thing to do is to include alternate hypotheses; or at least mention some possible confounding circumstances.

Many SE research papers include a "threats to validity" section which is more or less what you're describing

As i mentioned elsewhere, the spanish league 19-20 followed the first VAR season.

There were many adjustments to VAR heading into the Covid season. I would flag that as confounding factot

I wonder how that could be tested ?

Make the home audience cheer for home team penalties and boo for opponent penalties and measure the outcomes maybe?

Does Philadelphia have a soccer team?

They do! Kevin Durant is one of the owners.

I see what you did there.

You’d need to make the referees blind to which team’s stadium was home.

My best shot: blindfold the referees, put them in cars, drive them to random stadiums (of teams they have never refereed and have never seen the inside of - so preferably in a different country)*, put noise-cancelling headphones on them and dress all fans in white shirts.

* or use a different stadium but fill it with more home than away supporters? But then perhaps the home effect relies on it being the home stadium.

Um, any professional referee that cannot tell what stadium they are in clearly are not familiar enough with the sport to be a referee

Have the games scored by impartial evaluators who know the rules well. This should work well, provided the games are recorded on video anywhere.

For best results you'd need special video with several fixed vantage points, not video that follows the ball or the refs' attention.

Every professional sport in America has this specifically for coaching and analysis, so I can't imagine that the top-tier European leagues (at minimum) don't have access to something similar.

The Premier League requires 20-30 cameras depending if it's being broadcast live or not.

Appendix 3 (page 497) has detailed specifications on what type of cameras go where in the ground and what they should be pointing at, etc.

https://resources.premierleague.com/premierleague/document/2...

Even with imperfect video, any errors would not be biased towards any team.

I bet you can get most of the answer by checking for changes in two stats that can be empirically calculated: # of ground tackles and # of true offsides. Both could be algorithmically done provided decent footage.

You could have referees who aren’t in the stadium with the fans making the calls? Basically a squad of Larry Middleman[1] & George Bluth referees.

[1]https://arresteddevelopment.fandom.com/wiki/Larry_Middleman

Compare with “home” games that aren’t really home games? For example, Manchester City had a home game in Budapest this year (https://www.bbc.com/sport/football/56343751)

Clubs also sometimes are banned from playing in their own stadium, or can’t play there because it is being renovated.

Another idea: look at Inter Milan versus AC Milan or Genoa vs Sampdoria matches. Those clubs share a stadium, so they play their away games in their home stadium and vice versa.

You could also look at players who, after a decade or more at a club, switch clubs and soon thereafter return to their former home stadium to play an away match (yes, yet another confounding factor, and such players are extremely rare in today’s football)

Home team referee bias is well known across many sports.

If you Google it, you may find helpful studies like this one https://www.sciencedaily.com/releases/2007/04/070403112044.h...

From your link:

> Boyko studied the number of goals scored by a team at home versus those scored while away, and found that teams scored 1.5 home goals on average, and 1.1 while away.

Players seems like they would have much more of an effect on goals compared to referees. Players can equally be affected by crowds.

It seems very hard to separate the effects so you can show referee bias. The linked page does not show anything that confirms that referees rather than players are affected.

The very next paragraph reads:

> In addition to affecting the number of goals scored, the away team received more penalties, implying that referees are making calls in favor of the home team, possibly as a result of the influence of the crowd. Some individual referees are more susceptible to these influences than others. In fact, more experienced referees are less biased by the impact of a large audience, which suggests that they may develop a resistance to effects of the crowd.

The parent's point is that studies such as this don't fully account for the potential for players behaving better because they are at home.

I don't think that is the complaint. Referee bias is just human nature. People have a hesitancy to make a decision that will immediately cause tens of thousands of people to scream at them. That likely is the primary explanation here. Yet there is nothing done to isolate the refs outside of just averaging play among leagues and assuming that takes care of differences in play style. However players are impacted by fans just like referees. There can be a reasonable hypothesis that visiting players play less aggressively in empty stadiums which could also explain some of the observed changes. The numbers included in the article are not enough to draw conclusions on what is causing these changes.

Sports referees should relish that, knowing they are correct and empowered.

Often I feel that the commentary to science has a lot of what-if pedantry beyond that which is reasonable.

I am unsure how you would address this what-if issue. It's not a variable that can be measured or controlled easily and the means of measuring that would be up for contention.

Sometimes things aren't as complicated as people make them want to be.

Without inquisitive rigor, the hypothesis offered by the study author is also merely "what if pedantry".

Good scientific papers explicitly state what you can and cannot conclude from the data. Even if it is a case of "this is the best we can do" because there's no data to address the omitted variable, that should be clear.

I have a PhD in an area where (a) it's difficult to conduct experiments, and (b) it's often hard or impossible to get data for some variables. No one likes the person who critiques a paper presentation by saying, "you're not controlling for variable x" without providing a reason why it's an omitted variable and how you can proxy for it (if it's not directly available). But you also won't get far if you aren't clear about the limitations of your paper.

If it can’t be measured or controlled then conclusions which forgo it are not valid!

Punching a serious hole in the logic is hardly “ what-if pedantry”

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