2015 - Round 3 : Two-Goal Gazza

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The relatively late withdrawal of Gary Ablett from the Suns team to play the Cats on Sunday provided a fascinating case study this past week in how bookmakers value such pivotal players.

Prior to the formal announcement of his unavailability the Head-to-Head market for the game on the TAB had been Geelong $1.25 and Gold Coast $4.00, which made the Suns about 24% or 4 goal underdogs. Once the news had been confirmed and the relevant markets suspended for a few hours as a mark of respect, the TAB re-opened betting with the Head-to-Head market now at Geelong $1.14 and Gold Coast $5.75. The Line market was also posted with the Suns as 6 goal underdogs.

So, the absence of a single Suns player was assessed by the TAB as increasing the Cats' expected victory margin by 50% and their probability of victory by about 7% points. That, frankly, is extraordinary to me - but then so is Gazza and so are his skills. I can't help but feel though that surely no player, however gifted, is that influential on the outcome of a game involving 44 players. Others will, no doubt, have a different opinion.

Anyway, many of you are no doubt here not to read about the minutiae of market movements for a single game during the week, but instead to read about the weeks' wagers and tips. So, here are the former.

Investors have, as they did last week, just two head-to-head bets, this week the two totalling just over 3% of the Head-to-Head Fund. Both bets are on underdogs, the larger on the narrowly underdog Roos at $2.10 facing Port Adelaide on Saturday, and the smaller on the more lucratively-priced Eagles at $3.15 facing Fremantle on Sunday.

Those two head-to-head bets are accompanied by six line bets - also the same number as we had last week - three on favourites offering between about 7 and 8 goals start, and three more on underdogs receiving between about 1 and 3 goals start. Combined, the eight wagers represent a little under 6% of the Overall Portfolio.

Three contests, the home games for the Pies, Blues and Cats, carry no wagers at all, while only two, the Kangaroos v Port Adelaide and West Coast v Fremantle clashes, carry both head-to-head and line wagers. Those two games represent the weekend's largest upsides and downsides, a Roos win promising a 1.8c gain and defeat by 5 points or more threatening a similar-sized loss, and an Eagles win heralding a 1.2c gain, while a defeat by 19 points or more looms as a potential 1c loss.

Each of the four other games in which Investors are invested (as so, therefore, invested) carry 0.7c upside and 0.8c downside. All told, the round offers a maximum upside of about 6c and a maximum downside of about the same amount.

HEAD-TO-HEAD TIPSTERS

It's the Geelong v Gold Coast game that's generating the highest levels of disagreement amongst the Head-to-Head Tipsters this week, the final collective verdict being 16 votes for Geelong and 14 for Gold Coast. In political terms that would surely be considered a "swinging" verdict, which seems oddly appropriate for an activity involving cats (well, Cats anyway). 

For no other contest has the lesser-favoured team attracted more than nine supporters. In that game with the nine alone, Tipsters are prophesying an upset Saints win over the Pies on Friday night. All nine are Heuristic Tipsters though, notably, BKB is not amongst them.

BKB is, however, amongst the minority six Tipsters selecting a Port Adelaide win over the Kangaroos, the TAB bookmaker having installed Port Adelaide as narrow favourites. Five Tipsters also foresee a Dogs upset win over the Hawks, and five more envision a similar result for the Lions over the Tigers.

Home Sweet Home has this week's highest Disagreement Index of 40%, a little ahead of Easily Impressed I's 34%. A number of Tipsters share the week's low Index of 10%. Overall, the Disagreement Index for the week is 18%, which is well down on last week's 28% but still up a little on Round 1's 12%.

MARGIN PREDICTORS

The highest levels of disagreement amongst the Margin Predictors have also been recorded for the Cats v Suns contest, where the H2H family have gone as far as to predict narrow Suns victories. Combo_NN1 sees the game very differently though, and tips a 12 goal Cats victory.

Influenced heavily by that Combo_NN1 prediction, the range of margin predictions in the Cats v Suns game spans 13 goals. The Mean Absolute Deviation (MAD), which is far less influenced by that single prediction, is still also almost 3 goals - more than double the MAD for any other game.

The Adelaide v Melbourne and Hawthorn v Western Bulldogs games have the next-largest MADs, both of 8.3 points per Predictor. For those games, however, the debate is all about the margin of victory and not the owner of it. 

Where there is some debate amongst the Margin Predictors about who wins is in the Roos v Power game where eight Predictors have provided a negative margin of around a goal, and in the Lions v Tigers matchup where three have opted for a Lions win by about the same amount.

A number of Predictors have similarly high levels of disagreement with the consensus this week, but the two highest are C_Marg (11.3 points per game) and Combo_NN1 (11.2 points per game). Bookie_9 (3.0 points per game) and Combo_7 (3.5 points per game) have by far the smallest levels of disagreement this week.

Overall, the week's all-Predictor MAD comes in at 7.2 points per game, a little less than last week's 8.8 points per game, and somewhat higher than Round 1's 5.3 points per game.

PROBABILITY PREDICTORS

The Head-to-Head Probability Predictors reflect the MoS zeitgeist this week, returning a whopping 48% range and a 17% MAD in their predictions for the Cats v Suns game.

Relatively large MADs are also in evidence for the Roos v Power (11%), Lions v Tigers (6%), Eagles v Dockers (5%) and Blues v Dons (5%) games.

Again this week, the 25% cap rule has been invoked for one of the H2H probability assessments resulting in an H2H_Adjusted prediction in the Kangaroos v Port Adelaide game of 70%, some 5% below the H2H_Unadjusted figure. (The H2H assessment of the Cats' chances is also significantly lower than the TAB's but, as mentioned last week, exceptionally low assessments of a home team's chances are not subject to adjustment.)

Because of those aberrant assessments, H2H_Unadjusted has the week's high MAD at 7.8%. H2H_Adjusted, whose MAD is reduced a little by the adjustment in the Roos v Power game, still has the round's equal-2nd highest MAD at 7.3%, tied with C_Prob.

The all-Predictor average MAD for the round is 6.0%, well below last week's 10.6% and also a mite below Round 1's 7.1%. Unlike the Head-to-Head Tipsters and Margin Predictors then, the Probability Predictors find themselves, on average, more in agreement this week than in either of the previous two weeks. 

The Line Fund algorithm rates the Swans, Roos, Lions and Hawks all as about 65% or higher chances of winning on the line market this week. It also rates the Crows as about 57% chances, but considers the remaining contests as near coin-tosses.