This year I am participating in Simon Gleave‘s Premier League prediction competition. It is an interesting initiative, as both statistical models and and more informal approaches are compared.
Last time I participated in something like this was midway trough the last Premier League season for statsbomb.com’s compilation. This time, however, the predictions are made before the first match has been played. To be honest, I think it is futile to try to model and predict an unplayed season since any model based only on previous results will necessarily reproduce what has already happened. This approach will work OK for predicting the result of the next couple of matches midway trough a season, but making predictions for the start of a season is really hard since the teams have brought inn some new players and gotten rid of other and perhaps also changed managers and so on. And not to forget that we also try predict results 9 months into the future.
When May comes and my predictions are completely wrong, I am not going to be embarrassed.
Last time I wanted to use the Conway-Maxwell-Poisson model, but I did not get it to work when I included data from several seasons plus data from the Championship. I still did not get it to work properly, but this time I tried a different approach to estimate the parameters. I ended up using a two-step approach, where I first estimate the attack and defense parameters with the independent Poisson model, and then, keeping those parameters fixed, I estimated the dispersion parameter by itself.
To fit the model I used Premier League data from the 2010-11 season to the 2015-16 season. I also included data from the 2015-16 season of the Championship (including the playoff) to be able to get some information on the promoted teams. I used the Dixon-Coles weighting scheme with \(\xi = 0.0019\). I used a separate parameter for home field advantage for Premier League and the Championship. I also used separate dispersion parameters for the two divisions.
I estimated the dispersion parameter for the Premier League to be 1.103, about the same as I previously estimated in some individual Premier League seasons, indicating some underdispersion in the goals. Interestingly, the dispersion parameter for the Championship was only 1.015.
Anyway, here are my projected league table with expected (or average) point totals. This is completely based on the model, I have not done any adjustments to it.
|West Bromwich Albion||39.21|