Experts and the Crowd - Margin predictions

Having taken the plunge and signed up for the Footy Mathis Institute Margin Tipping competition (first prize: bragging rights; last place potential ridicule) I have decided to try and understand margins a bit more.  Previously I focused on first pass the post win/ loss tipping but have used the margin predictions from my model to estimate the odds which in turn I use to compare where I have a difference of opinion to the bookies.



So aside from looking at my fellow Footy Maths tipsters and the collection of like minded internet bloggers (Footy Forecaster, Matter of Stats and Tip Bet Pro) I have started to pay more attention to the "Expert" tips in The Age and the Herald Sun (ignoring the Village Idiot etc).  Having entered the numbers for the first three rounds I am surprised at how poor the margin tipsters are - and how very poor my margin tips have been.  Of the 1761 margin predictions a total of 21 have been spot on and 231 within 6 points (Notably Footy Forecaster picked two correct margins in Round 2).  When I plot the cumulative percentage of the difference between the predicted and actual margins I was very surprised to see an essentially straight line (with 50% within a 5 goal margin and the other 50% up to about 100 points off the mark!)







Moving onto the second item of interest is how many of each rounds actual results fall outside the range of predictions.   Looking at round 1 for an example it is obvious to all that GWS beating Sydney was very unexpected.  But Collingwood being opened up by Fremantle was as unexpected based on the distance from the actual result to the nearest prediction from the experts.  None of the experts came close to predicting Essendons victory over the Roos or the Bulldogs loss to the West Coast.  Add to that the result of Gold Coast over Richmond almost falling outside the experts prediction window and you really need to re think how expert the collection of experts are.







rounds 2 and 3 do not fair much better:



Round 2: Port, Sydney and West Coast all outside the experts range.





Round 3

Hawthorn, Adelaide, Gold Coast and Essendon are outside and Bulldogs only fall in as I assigned Murphy a ten point victory margin for his team (probably should remove this from the analysis)









 

So all up twelve games actual results fell outside of the range of predictions from 75 Experts.



I am intending to look at the relationships with average margin predictions, bookies odds and whether the tipping accuracy improves over the season over the coming weeks but to date I think it is fair to say the expert opinion should be called the expert guess.