Regression to the mean can be a bitch! (Ask the nearest Blackpool fan)

I’ve wanted to do a post about Blackpool for a while and I think they give me a perfect example to demonstrate a few things I’ve been talking about recently. In particular they are the perfect model of regression to the mean in action.

After a flying start to the season they’ve sunk rapidly down the league and now sit in the relegation zone. This can be explained by looking at their PDO. I’ve already shown that PDO regresses strongly to the mean on a season by season basis and below is a plot of Blackpool’s PDO this season (remember the mean in this case is 1000)

Early on (when they scored a lot of points) their PDO was high (staying above 1200 for the first 5 games). Since then their PDO has regressed heavily to the mean and the rate at which they have scored points has also slowed, as shown below.

They track each other perfectly but intuition tells us that should be the case, whilst your getting lucky (high PDO) you tend to score points and when your being unlucky (low PDO) they tend to dry up. And that is the beauty of regression to the mean. Teams as poor as Blackpool can go on a remarkably good run but over the course of a long season the luck simply runs out and we see a pretty good reflection of their true ability.

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