2016 - Team Ratings After Round 4

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Though it's hard to argue with the efficacy - so far - of the forecasting systems built using the ChiPS and MoSSBODS Team Ratings, I'm still getting used to how readily the two Systems are willing to adjust their opinions about a team on the basis of a single week's results.

That behaviour will abate soon enough, since ChiPS will use about a 40% lower Ratings adjustment multiplier from Round 7 onwards and MoSSBODS will use a 33% lower multiplier commencing in Round 8. In the meantime we should all be prepared for more sometimes largish movements. It's all about properly weighting the class embedded in a team's current Rating and the ability revealed in more recent form, and history tells us that we should place a relatively higher emphasis on form in the early parts of the season.

So it is that ChiPS re-ranked 13 of the 18 teams this week, seven of them by multiple spots. GWS led the climbers, rising three spots into 7th, while St Kilda and Melbourne both enjoyed two spot climbs into 12th and 13th respectively. Richmond were the biggest fallers, slipping three places into 9th, Hawthorn, the Gold Coast and Collingwood all dropping two spots into 3rd, 14th and 15th respectively.

In terms of Rating Points (RPs), the big movers were GWS and Port Adelaide, with over 11 RPs being transfered to the former from the latter. That means there's now almost a 10 RP gap between the 9th-placed Tigers and the 10th-placed Power.

MARS was slightly more circumspect in its re-evaluations (it uses the same Ratings adjustment multiplier for the entire season), re-ranking only 10 teams, and only two by more than a single place. Those two multi-spot movers both rose, West Coast climbing into 1st place and GWS into 10th.

That leaves ChiPS and MARS differing by two places or more in their Rankings for just six teams:

  • Sydney - Ranked 3rd by MARS and 1st by ChiPS
  • GWS - Ranked 10th by MARS and 7th by ChiPS
  • St Kilda - Ranked 15th by MARS and 12th by ChiPS
  • Port Adelaide - Ranked 8th by MARS and 10th by ChiPS
  • Gold Coast - Ranked 12th by MARS and 14th by ChiPS
  • Collingwood - Ranked 13th by MARS and 15th by ChiPS

Despite all the apparent upheaval then, the two Systems do still broadly agree about most team's abilities, a fact that is reinforced when we calculate the linear correlation between their raw Ratings: it's +0.95.

MoSSBODS Ratings

MoSSBODS was much more ChiPSotic than MARSian this week, changing the Combined Ranking of all but three teams, two by as many as four places.

Port Adelaide and Gold Coast were the teams moving furthest, both slipping four places. Defensive Rating declines contributed most to both teams' declines, Port Adelaide dropping six places after conceding 41 Scoring Shots to GWS, and the Gold Coast dropping five places after conceding 37 Scoring Shots to the Lions.

The Western Bulldogs were another of the big decliners, they dropping three places into 4th on Combined Rating after their Offensive Rating took a battering courtesy of a paltry 20 Scoring Shot haul against the Blues. Richmond were the only other team to slip multiple places, they falling from 11th to 13th Combined, based on decreases in both their Offensive and Defensive Ratings and Rankings.

Five teams climbed three places on Combined Ratings this week, including West Coast who, in doing so, grabbed the number 1 Combined Ranking. They are now rated almost a two-and-a-half Scoring Shot better team than any other in the competition.

GWS also rose three places overall into 6th, their elevation mostly attributable to a substantial lift in their Offensive Rating emanating from their 41 Scoring Shot performance against Port Adelaide. The Lions were another team to rise three places overall mostly on the back of unexpected Offensive output, while the Saints and the Blues rose three places overall after producing unexpectedly good Defensive performances.

We can get a perspective on the size and nature of each team's Rating changes as a result of Round 4 results from the chart below (which really needs a name - how about the Team Ratings Weather Vane?)

One thing I find that this chart makes clear fairly readily is the teams that have the best and worst Ratings on the two dimensions. Adelaide, we see, has the highest Offensive Rating, and Essendon the lowest, while the Western Bulldogs have the highest Defensive Rating, and the Brisbane Lions the lowest.

It's also allows us to quickly identify the teams whose Offensive and Defensive Ratings both increased from the start of the round to the finish; they're the ones with arrows pointing north-east - West Coast, GWS, Geelong and the Brisbane Lions. Conversely, teams with arrows pointing south-west are those that saw their Offensive and Defensive Ratings decline - Port Adelaide, Gold Coast, Richmond and Essendon.