Another 7 out of 9 games went to the home team last week. This brings the total home team wins for the year to 21 out of 27 games. You would be there abouts in most tipping competitions if you had just picked the home team for every match and just left it at that. 1
Do we expect that sort of home team dominance to continue this week? Well, not really. With Essendon, Brisbane and Carlton all playing at home against reasonable opponents on Saturday, I would be very surprised if we had another big round for the home teams.
This round really breaks down into three distinct types of matches. The one-sided (ESS v GEEL, HAW v STK, BRIS v GCS, CAR v WBD), the genuinely tight (ADE v SYD, GWS v PORT, COLL v MELB) and the buggered if I know (WCE v RICH, NTH v FREM). For the first time this season, FFSS thinks she has spotted value in the betting markets for every game. I on the other hand, am not so sure.
I have translated calculated probabilities into inferred match odds and compared these to the current prices offered by some of the bigger bookmakers around the country, highlighting any major discrepancies. The reason I have done this is not to recommend or even advocate having a bet on any particular team (although I will certainly talk about “good bets” and “value”). But it is rather used as a way to explore the strengths and weaknesses of the model in greater detail.
Bookie prices can be seen as a general “public consensus” about what the true probabilities of a team winning a match are. When the model differs greatly from the public view it is good to know why. Is it seeing something else that the public are not valuing? Or, as you’ll see this week, is it missing entirely something that others are taking into account? If it’s the latter, then there is clear improvement that can be made, if the former, then I guess we’re on to a winner.
All betting amounts will be discussed as unit bets assuming you have 100 units to play with as your full bankroll. For example if you have $1000 that you’re willing to lose over the year if worst comes to worst, then 1 unit is $10. A higher unit bet shows more confidence in the models assessment and the value to be made. If you are interested in betting as a serious money building exercise, first I would question whether you really want to cope with the stress of the virtually guaranteed big losses you will experience week to week. If the answer to that is yes, then read as much as you can on Bankroll Management and the fractional Kelly Criterion. You are very likely betting too much to be sustainable.
The graphic above highlights all of FFSS’s probability estimates for the week. The prices next to each team are the minimum suggested price to take if you were to bet on them to win the match, assuming that FFSS predictions are perfect. In reality this is, of course, very likely not so.
The graphic opposite shows the FFSS team ratings at the start of the round. These, along with a concession for Home Ground Advantage are the direct inputs for the final probability estimates.
Rather then write previews for every match of the week, I will instead comment on interesting discrepancies between bookie odds and FFSS odds, why these may exist, and whether there is any value in betting at the available price.
Essendon v Geelong
Every week FFSS thinks there is value in an Essendon bet and every week I have to step in and return order, reminding everyone that she doesn’t really know about the WADA bans yet. “Give it a few weeks for FFSS to update her ratings” I keep saying. Well it has been a few weeks now, the Bombers still aren’t considered the worst team in the comp and some bookies are offering a massive $13 on Essendon.
Make no mistake about it. I think Geelong will win this game and win it comfortably. But $13 will coax me into a tiny tiny little flutter on (a still unknown) Essendon for the first time this year.
Bet 0.5 Units on Essendon @ $13 – Sportsbet, William Hill, Palmerbet, Unibet
Hawthorn v St Kilda
FFSS thinks the Saints have about a 18% chance this week. The bookies think about 12.5%. Could be some very small outsider value here again.
Adelaide v Sydney
This is the first interesting prediction of the week (and not just possible slim outsider value like the first 5 matches). The bookies have the Swans going in favourites, but FFSS is 60% confident in her assessment that Adelaide will get the job done at home.
There are not too many personnel changes for this match, outside of running forward Tom Lynch coming back into the Crows side after the birth of his daughter last weekend. So that’s not a reason for the discrepancy.
There may still be some lingering affect of Adelaide’s rating being based of Dangerfield included in their side last year and Sydney’s being a bit depleted due to the lack of Buddy late last year. However, the majority of that should have smoothed out by now and it won’t stop me from backing FFSS’ assessment and getting on the Crows at 2.02.
Bet 4 Units on Adelaide @ $2.02 – Sportsbet
GWS v Port Adelaide
There is a lot of hype surrounding GWS given they have lost 2 out of their 3 games (including Round 1 to Melbourne). In contrast, people have gone right off Port despite them only having lost 1 game (the Showdown against Adelaide) so far in 2016.
Both FFSS and I understand that the Giants have beaten quite a good team in Geelong, and Port have really yet to claim a major scalp. And I (but not FFSS) understand that Port have been having some serious injury troubles.
However, without considering any player changes FFSS considers the Power a 58% chance of winning, while some bookies only give them a roughly 46% chance. This being considered, I think there is definitely some value in a bet on Port.
Bet 3 Units on Port Adelaide @ $2.15 – William Hill
Collingwood v Melbourne
Collingwood continue to under impress. Melbourne continue to be Melbourne. I continue to back FFSS’ assessment that there is some slight value in Melbourne as outsiders at $2.50.
Bet 2 Units on Melbourne @ $2.50 – bet365
North Melbourne v Fremantle
I’ve heard a few times this week that Freo are “due for a win” and hence might be a chance this week. I’m not exactly sure how I feel about this sentiment. It is true that in the scope of their respective seasons, this game is much more important for Freo than it is for North, but whether this means that they are more likely to win then they would have been if the roles were reversed I am not convinced.
After studying probability for a while, you begin to realise that a lot of what you thought was true happens to just be a quirk of luck (i.e. a probability distribution).
There was a bit of debate on Twitter this week regarding whether “momentum” was a real concept or just a narrative written after the fact.2 Can you predict momentum before it happens? If a team has been winning (and we somehow know the exact “true rating” of that team) are they more likely to win the next game? If you have flipped heads 3 times in a row, are you more likely to flip heads next time? Is it fair to compare these two events?
The “due for a win” strikes me as the exact opposite of momentum. A team has been playing badly therefore it is now time for them to play well? Yet the two are often used by the very same pundits. I’m skeptical, but not decided on whether there is value in using this sort of analysis. More research needs to be done.
As for the game, Sandilands is out, Goldstein will dominate, I think there is definite value in a $1.42 bet on North at an implied win probability of roughly 70%.
Bet 4 Units on North Melbourne @ $1.42 – Luxbet