MAFL 2010 : Round 27 (or GF 2.0)

Every so often things crop up that unexpectedly test the statistical models I've constructed. For example a client will ask for a model to be used for a practical purpose such as forecasting, or they'll ask me to rerun a set of scenarios that I've created using a model, but this time with slightly different inputs.

Drawing On Hindsight

When sports journos wait until after a contest has been decided before declaring a group of winning punters to be "savvy", I find it hard not to be at least a little cynical about the aptness of the label.

The Bias in Line Betting Revisited

Some blogs almost write themselves. This hasn't been one of them.

It all started when I read a journal article - to which I'd now link if I could find the darned thing again - that suggested a bias in NFL (or maybe it was College Football) spread betting markets arising from bookmakers' tendency to over-correct when a team won on line betting. The authors found that after a team won on line betting one week it was less likely to win on line betting next week because it was forced to overcome too large a handicap.

MAFL 2010 : Round 26 Results (of a fashion)

After that it all feels a little flat.

I just assumed there'd be extra time on Saturday and at least an attempt to find a winner on the day; making 44 players, 2 coaching staffs, 100,000 spectators and countless fans go through that all again seems cruel, unusual and frankly unnecessary.

Grand Final History: A Look at Ladder Positions

Across the 111 Grand Finals in VFL/AFL history - excluding the two replays - only 18 of them, or about 1-in-6, has seen the team finishing 1st on the home-and-away ladder play the team finishing 3rd.

This year, of course, with be the nineteenth.

MAFL 2010 : Round 26 (Week 4 of the Finals a.k.a The GF)

There'll be no dramatic last game plunge into profitability for any Investor this season.

The best that Investors with the Recommended Portfolio can hope for is to end the season down by about 4.5%, and it'll take a Pies victory in the GF by 17 points or more to deliver them that result.

Adding Some Spline to Your Models

Creating the recent blog on predicting the Grand Final margin based on the difference in the teams' MARS Ratings set me off once again down the path of building simple models to predict game margin.

It usually doesn't take much.

Pies v Saints: An Initial Prediction

During the week I'm sure I'll have a number of attempts at predicting the result of the Grand Final - after all, the more predictions you make about the same event, the better your chances of generating at least one that's remembered for its accuracy, long after the remainder have faded from memory.

MAFL 2010 : Round 25 Results (Week 3 of the Finals)

As predicted, the haloed and the winged triumphed over the furry this weekend, leaving us with a Pies v Saints Grand Final for only the second time in VFL/AFL history.

Presumably there are supernatural consequences of cursing saints, but it was difficult to avoid risking them on Saturday night if you were a MAFL Investor watching the game as the Saints went marching off and allowed the Dogs to tack on just enough late points to win on line betting by half a point.

That cost the Recommended Portfolio almost 1% and meant that it increased by only 2.2% over the two games. This leaves the Recommended Portfolio down by 6.4% on the season on the back of three straights weeks of profitability during the Finals.

Visualising AFL Grand Final History

I'm getting in early with the Grand Final postings.

The diagram below summarises the results of all 111 Grand Finals in history, excluding the drawn Grand Finals of 1948 and 1977, and encodes information in the following ways:

• Each circle represents a team. Teams can appear once or twice (or not at all) - as a red circle as Grand Final losers and as a green circle as Grand Final winners.
• Circle size if proportional to frequency. So, for example, a big red circle, such as Collingwood's denotes a team that has lost a lot of Grand Finals.
• Arrows join Grand Finalists and emanate from the winning team and terminate at the losing team. The wider the arrow, the more common the result.

No information is encoded in the fact that some lines are solid and some are dashed. I've just done that in an attempt to improve legibility. (You can get a PDF of this diagram here, which should be a little easier to read.)

A Proposition Bet on the Game Margin

We've not had a proposition bet for a while, so here's the bet and a spiel to go with it:
"If the margin at quarter time is a multiple of 6 points I'll pay you $5; if it's not, you pay me a $1. If the two teams are level at quarter-time it's a wash and neither of us pay the other anything.

Now quarter-time margins are unpredictable, so the probability of the margin being a multiple of 6 is 1-in-6, so my offering you odds of 5/1 makes it a fair bet, right? Actually, since goals are worth six points, you've probably got the better of the deal, since you'll collect if both teams kick the same number of behinds in the quarter.

Deal?"

MAFL 2010 : Round 25 (Week 3 of the Finals)

If you've been following the story so far and I were to tell you that there are two home-team favourites this weekend, one of them short-priced, you should be able to guess the behaviour of at least two of the Funds that are still trading.

All You Ever Wanted to Know About Favourite-Longshot Bias ...

Previously, on at least a few occasions, I've looked at the topic of the Favourite-Longshot Bias and whether or not it exists in the TAB Sportsbet wagering markets for AFL.

Divining the Bookie Mind: Singularly Difficult

It's fun this time of year to mine the posted TAB Sportsbet markets in an attempt to glean what their bookie is thinking about the relative chances of the teams in each of the four possible Grand Final pairings.

Simulating the Finals (After Week 2 of the Finals)

Another week, another 1,000,000 simulations.

This week it's a relatively brief summary, since there are only four teams remaining and because TAB Sportsbet no longer has markets for teams' chances of making the Grand Final nor for the possible Grand Final pairings.

MAFL 2010 : Round 24 Results (Week 2 of the Finals)

Maybe MAFL should only operate during the Finals.

The Cats and the Dogs delivered almost to order for MAFL Investors in their respective Semis, the only losing bet coming as a consequence of the Dogs falling just two points short of covering their 6.5 points spread.

This meant that the Recommended Portfolio rose by 2.2c to 91.49c and MIN#017's Portfolio jumped 7.65c to 48.46c. With no action this weekend MIN#002's Portfolio remained unchanged at 72c.

Just Because You're Stable, Doesn't Mean You're Normal

As so many traders discovered to their individual and often, regrettably, our collective cost over the past few years, betting against longshots, deliberately or implicitly, can be a very lucrative gig until an event you thought was a once-in-a-virtually-never affair crops up a couple of times in a week. And then a few more times again after that.

MAFL 2010 : Round 24 (Week 2 of the Finals)

Each season as we enter the Finals and games take on heightened historical relevance, a part of me wishes that the MAFL Funds would sense the occasion and respond accordingly by doing something dramatic and memorable.

They never do, of course, partly because they're not sentient and partly because the opportunity for winning large sums of money on huge home-team underdogs rarely arises during the Finals. As far as the Funds are concerned, the Finals are just another round offering a few more opportunities to spot and exploit mispricing in the head-to-head and line markets.

Which Teams Are Most Likely to Make Next Year's Finals?

I had a little time on a flight back to Sydney from Melbourne last Friday night to contemplate life's abiding truths. So naturally I wondered: how likely is it that a team finishing in ladder position X at the end of one season makes the finals in the subsequent season?

Simulating the Finals (After Week 1 of the Finals)

Okay, six teams left, and you know the drill.

Here's the probability matrix I'm using this week (and again we're ignoring any home ground benefits):

Running the now customary 1,000,000 simulations using this matrix gives us the probabilities shown in the tables below. The rows labelled "Fair" contain fair value prices and those labelled "Offer" contain the most-recent TAB Sportsbet prices.

Double-asterisks denote those wagers that the simulations suggest represent value. As has been the case for a while now, the simulations suggest that the Dogs represent value in both the Flag and the Plays-in-the-GF market.

As well, the Cats are a value bet at $4 for the Flag; the simulations suggest that any price over about $3.30 for them represents value.

In contrast, Sydney and Freo represent appalling value at only $13 and $41 respectively. You'd instead want about $30 and $125 respectively to feel as though you were obtaining fair value for this pair.

Lastly, a look at the GF Quinellas, where you'll notice that only 9 possible Grand Final pairings remain possible:

Here, the value combinations are indicated by green shading, and all of the value bets involve the Dogs.

Whether the Dogs are value bets or not all still comes down to the extent to which you believe that the Dogs' recent performances are the best indicators of their likely performance next week and, if they survive, in the weeks that follow.

MAFL 2010 : Round 23 Results (Week 1 of the Finals)

MAFL's generally done well during the Finals and, while it could have been better had the Cats' final goal been allowed to stand and had the Swans managed more than 3 behinds in the 3rd term, this year's September has at least started in the black.

Coast-to-Coast Blowouts: Who's Responsible and When Do They Strike?

Previously, I created a Game Typology for home-and-away fixtures and then went on to use that typology to characterise whole seasons and eras.

In this blog we'll use that typology to investigate the winning and losing tendencies of individual teams and to consider how the mix of different game types varies as the home-and-away season progresses.

2010: Just How Different Was It?

Last season I looked at Grand Final Typology. In this blog I'll start by presenting a similar typology for home-and-away games.

MAFL 2010 : Round 23 (Week 1 of the Finals)

The importance of the weekend's fixtures should have all of us curious about their outcomes. If you're a Recommended Portfolio holder, though, and you're a bit concerned that one or two contests might drift into dullness, be comforted by the fact that you've wagers in all four.