Matter of Stats

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2018 - Round 16 : Overs/Unders Update

Last weekend's unexpectedly high-scoring round has done little to raise hopes for a repeat this weekend where we find both bookmakers' average expected margin coming in at just 166 points per game. 

The MoS twins have similar overall expectations, and forecast, like the bookmakers, that only three or four games are likely to top 170 points in aggregate, but they do have some unusually large differences of opinion with the bookmakers in a couple of games, most notably the Essendon v Collingwood game where the forecast of rain (and possibly hail) has doubtless had an influence. More on that later.

MOST LIKELY HIGH-SCORING GAME

  • MoSSBODS, TAB and Centrebet : North Melbourne v Gold Coast (177 to 178.5)
  • MoSHBODS : Melbourne v Fremantle (176)

MOST LIKELY LOW-SCORING GAME

  • MoSSBODS and MoSHBODS : Sydney v Geelong (154 to 156)
  • TAB and Centrebet : Essendon v Collingwood (148.5 to 149.5)

MOST LIKELY HIGH-SCORING TEAM

  • All : North Melbourne (111 to 114)

MOST LIKELY LOW-SCORING TEAM

  • MoSSBODS : Adelaide (61)
  • MoSHBODS : Gold Coast (61)
  • TAB & Centrebet : St Kilda (58)

MoSHBODS had some success relative to naive forecasting in selecting the extremes of team and game scoring last weekend, attaching:

  • 2.9% probability to the highest-scoring team, Essendon (against a naive forecast of 5.6% since 18 teams were playing)
  • 19.0% probability to the lowest-scoring team, Gold Coast (against a naive forecast of 5.6%)
  • 20.9% probability to the highest-scoring game, Melbourne v St Kilda (against a naive forecast of 11.1% since 9 games were played)
  • 2.6% probability to there being tied lowest-scoring games (Carlton v Port Adelaide and Gold Coast v Collingwood). It's hard to assign a naive forecast to this outcome.

This week, MoSHBODS has

  • six teams as more likely than 1 in 18 to be the highest-scoring: North Melbourne, Richmond, Port Adelaide, Melbourne, Brisbane Lions, and Collingwood.
  • six teams as more likely than 1 in 18 to be the lowest-scoring: Gold Coast, St Kilda, Adelaide, Geelong, Western Bulldogs, and Carlton.
  • four games as more likely than 1 in 9 to be the highest-scoring: Dees v Dockers, Dons v Pies, Roos v Suns, and Lions v Blues.
  • four games as more likely than 1 in 9 to be the lowest-scoring: Swans v Cats, Dogs v Hawks, Power v Saints, and Eagles v Giants.

WAGERS

Investors have four wagers this week, two unders and two of the troublingly unsuccessful overs.

In the first of those overs wagers - for the Port Adelaide v St Kilda game - the overlay is 6.5 points (although shown as 7.5 here because I have adjusted the Centrebet total to be the implied even-money total, which is one point different given that overs was priced at $1.91 when I placed the wager). There is, naturally, a forecast for rain in that game (albeit for "showers easing"). That's all fairly standard.

For the Dons v Pies game, however, the forecast of rain seems to have knocked a far larger chunk off the posted total, with the result that our estimated overlay is about four goals. I don't know how much rain constitutes four goals, but I'm hoping it's a lot.

There's also an atypically large overlay in the Dogs v Dons game, though there MoSSBODS is forecasting a much lower total than the bookmakers, so weather can't be hypothesised as the cause (and, in any case, the game is being played at Docklands). I'm at a loss to explain the sizeable difference here - other than to note that MoSSBODS rates both teams fairly poorly on offence and the Hawks well-above average on defence - and will be interested to follow movements in this total over the remainder of the week.

PERFORMANCE TO DATE

MoSSBODS finished on the correct side of the TAB's and Centrebet's totals in five of the nine games last weekend, while MoSHBODS finished on the correct side of both bookmakers' totals in only four.

That left MoSSBODS' with a season-long 49% record against the TAB and a 48% record against Centrebet, and left MoSHBODS with a 47% record against the TAB and a 50% record against Centrebet.

MoSSBODS' landed 0 of 1 unders bets with the TAB last weekend, and 1 of 2 overs bets with Centrebet. Its overall strike rate on overs bets is now 29% and on unders bets 60%.

On the mean absolute error (MAE) metric, MoSSBODS registered the lowest MAE for game margins (again) and for home team scores this week, while the TAB bookmaker did the same for away team scores and game totals. 

Centrebet still leads, however, on the season-long view for home team scores and game totals, while the TAB also still leads on game margins and away team scores.