Over the years, every time United win a penalty or one is not called against them - we hear the usual "The FA/refs are in United/Fergie's pocket". In fact, just today, Patrick Vieira - the City ambassador (how exactly an ex-Arsenal player who played for the club for a few months is now their ambassador is beyond me) - suggested that United get preferential treatment when it comes to PKs. There certainly have been many controversial penalty calls at Old Trafford. So, do the facts support this claim?
Telegraph article
The first set of statistics I found were from the Telegraph - a well respected newspaper (as respected as journos can be, I guess) - and it does not seem to support the United bias:
Link to telegraph article
For those of you who do not want to read through the link, let me summarize for you. You see, what the website does is gives an index score based on the # of penalties teams have conceded at home against the # of games played at home. Therefore, the higher the ratio, the more likely the team is to concede PKs at their home ground. The range is 0.05(Chelsea) to 0.17 (West Ham United). United comes in 8th out of 20 with a ratio of 0.07. This translates to - United concede 7 penalties out of every 100 games they play at Old Trafford.
As a scientist, I understand the power of statistics to manipulate/misrepresent data. Therefore, I comprehend these numbers in two ways:
1. United is more likely than many clubs (including Spurs, Liverpool and Chelsea) to concede PKs at home. (this is the easy interpretation).
2. United is neither more nor less likely than other clubs (especially the big clubs) to concede PKs at home - I would argue that a difference of ~0.02 is not really a statistical significant difference. I think this is the correct interpretation.
United-biased article
The next set of data I found was from a website run by United fans - so I understand that the analysis of the data can be annoying to read for non-United fans. I encourage you to skip through the rhetoric and head straight to the table:
Link to stretford-enders article
This is the analysis of the current season and reveals the # of penalties awarded for and against each team - both home and away. United has been awarded 5 penalties this season (2 at home and 3 away) and has had 6 penalties awarded against them (1 at home and 5 away). Compare that with any of the other big clubs and you will see that United do not seem to get preferential treatment.
Then why does this idea exist?
I'm not naive enough to think that people just make stuff up for the sake of it. I honestly believe that the people who say that United get more penalties at home and/or United don't concede penalties, say so because they actually believe it. I think that it is a case of a combination of two social psychology-related phenomena:
1. Confirmation bias - This is when there is a prevalent hypothesis and people interpret only data in line with this hypothesis. In our case, people notice when United win dodgy penalties/decisions and forget when decisions go against United.
2. Groupthink - The idea that since other people believe a hypothesis, it must be true.
I hope this clears the "United get favorable PK decisions" idea. I'm curious if anyone else has any data that supports that claim - I have not done enough research admittedly, but I didn't seem to come across DATA (not articles) that support the bias claim. Please feel free to share if you have...
