Alan Shearer riled up Analytics TwitterTM today with this comment:
— Alan Shearer (@alanshearer) November 7, 2015
Analytics TwitterTM hates these sorts of arguments, best summarized by @MessiSeconds response:
— Joel Salamon (@MessiSeconds) November 10, 2015
I’m confident Joel’s video response will be well-written, well-argued, and well-produced like the rest of his videos, but I think the answer is much simpler than this: at the end of the day, points are all that matter in the relegation fight, but we’re nowhere near the end of the day yet.
However, I’m going to depart slightly from what I assume the rest of Analytics TwitterTM is probably going to say. Alan Shearer is right: Three points for Newcastle over Bournemouth was a significant result, and changed my predicted final table in a significant way given it is only one result. Here’s the weekly heat map results from my model for the two teams:
The win moved Newcastle’s relegation probability down a few points, and moved Bournemouth a few percentage points closer to relegation. Regardless of the stats, this was a bad week for Bournemouth. Playing well isn’t much comfort in this case.
However, the stats tell a more nuanced version of Shearer’s point, ultimately leading him to the wrong conclusion. Newcastle doesn’t care about winning ugly this week, but in the long-run they do care that they won a game they in all likelihood shouldn’t have because that means they can expect to earn fewer points across the season. In a one-shot game, Newcastle is happy to have taken the three points from a relegation rival and they don’t have to give those back just because they were out-played. However, across a 38 game season, if they keep playing like this, the law of large numbers will probably catch up with them and they’ll be down in the Championship.1 It’s the reason Las Vegas casinos make billions of dollars: if the fundamental statistics are in your favor, in the long-term you can’t possibly lose.
Three points today are a victory today and no xG map can change that. Newcastle’s probability of staying in the EPL next year increased, and the points they earned stay on the table. The opposite is true for Bournemout: their probability of staying decreased, and the points they missed can never be made up. But in the long-run Newcastle’s manager knows that they got lucky and will have to improve if they want to avoid the drop. Alan Shearer likely knows that too, so we shouldn’t feed the troll.
- 38 is hardly what the law of large numbers folks had in mind as a “large number” but it’s close enough for our purposes. If you’re not satisfied with this explanation, then extrapolate it to multiple seasons until you get to a number large enough for your taste. ↩