## Sunday, 8 June 2014

### Enjoy the silence

I've been quite silent on the blog in the past few weeks $-$ a combination of exam-marking, conference-organisation and other few (some more, some less interesting) things...

As for Bayes Pharma, we're nearly there $-$ the conference is this week Wednesday to Friday. I've nearly got everything ready $-$ at least all I can think of, that is. We've arranged the social event (I'll post pictures, especially if the weather keeps good). The finalised programme with talks & titles is here. I'll post on how the conference progresses in the next few days.

On a totally different note, Marta and I have spent some time working on extending our football model to do some prediction for the impending World Cup. Lots of people have had a go (including some people at Goldman Sachs and others in the new Significance website $-$ eg here and here).

Unlike many, we won't try to predict the overall winner straight away $-$ I think that there are very good arguments to not doing that: 1) the stage group may significantly differ from the second stage; especially in a competition such as the WC, which is played over one month, the impact of current (or very, very recent form) can be dramatic.

So, what we'll do is:

1. Use past data (on the last 4 years of international games + the last 6 World Cups, in total about 3500 games) to fit an extended version of our model (which accounts for correlated "team" and "opponent" structured effects);
2. Use data on "current form" (based on the official bookmakers' odds) to predict the first round of games. The prediction can be assessed against the observed results which will become available in the first few games of the competition;
3. Update the variable of "current form" based on the observed results (so if a team unexpectedly win their first game their "form" is bumped up and they should be predicted to do better than they would have been with the previous data only). These new data can be used to predict the second batch of games (and so on for the third batch of data).
Once the group stage is over, we'll carry the predictions forward.

I'll post more details on the model and the results of the prediction exercise (including how well we're doing) in the next few days.