Continuing the theme of my last few posts. I’m going to continue looking at which metrics are repeatable at the team level over the course of a Premiership season. The series so far:
Today I’m looking at the award of penalties for and against a given team. The data set spans the 2001-02 – 2011-12 seasons. In total there are 220 team seasons, and 170 pairs of back-to-back seasons (17 non relegated teams per season X (11-1) seasons).
How repeatable is being awarded penalties?
Continuing in the recent vein, there’s not a lot of repeatability here – in short, the ability at the team level to win penalties over the course of a Premiership season is 96% luck driven and a mere 4% skill driven. Our best guess is basically that teams will get ~5 penalties next season, almost regardless of the number they took last time around.
Next let’s take a look at the number of penalties given against a team?
This time we have a larger skill component, but it’s still only 9%, whereas the other 91% is luck at the team level over the course of a Premiership season. Once more luck is by far the dominant factor, and we’re best off assuming that a team will concede ~5 penalties in a given season.
And finally, how about a teams penalty differential (penalties awarded for minus penalties awarded against) – is there any repeatability there?
Well there’s certainly more skill. But the breakdown is still a meagre 11% skill/89% luck at the team level over the course of a Premiership season. In this case, the best penalty differential (+9) is worth ~1 penalty per season – or ~0.77 goals. (Which marries well with last time, where I found that the best ‘penalty scored differential’ was worth ~0.65 goals)
In summary, the variance in the number of penalties awarded/conceded by a given team over the course of a season is very much dominated by luck rather than skill.
Finally, as for the last time around, it is worth saying that although 1000 penalties have gone into producing each plot, a given point still represents only a small number of penalties. In other words there’s scope for these numbers to move, but the correlations are so tiny that any movement would still leave luck as the overwhelmingly dominating factor.