2015 - Team Ratings After Round 15

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It was a week for tweaks rather than wholesale ChiPS re-Rankings as six teams were shuffled by just a single place and only one, St Kilda, was demoted by a couple of places.

Viewed in raw Ratings terms, the Hawks v Freo game produced the largest transfer of ChiPS Rating Points (RPs) as the Hawks' 72-point win was assessed by worthy of a 4.4 RP swap between the victors and the vanquished. The next largest transfer was the Roos' 3.1 RP gain from the Cats, then GWS' 2.5 RP gain from the Saints.

In other games, Sydney, despite winning, shed RPs, while the Eagles gained them, these changes, along with the Hawks' big gain, now leaving the Swans Rated as about 11 points weaker than the Eagles and about 18 points weaker than the Hawks.

MARS re-Ranked fewer teams than ChiPS - only six - but half of those it moved it did so by multiple places. The Roos and Port Adelaide both climbed two places into 8th and 7th respectively, while Geelong fell three places into 10th.

Those moves see the round finish with no team Ranked by ChiPS and MARS differently by more than two places, and only three teams differing by exactly that amount:

  • Richmond (Ranked 4th by ChiPS and 6th by MARS)
  • Melbourne (15th and 17th)
  • Carlton (16th and 14th)

As a result, the rank correlation between ChiPS' and MARS' team Rankings remains at a high +0.981.The correlation between their raw Ratings is also at a high +0.957. 

Rank correlations for the two Systems with the competition ladder ordering are now +0.901 for ChiPS and +0.889 for MARS. As far as ChiPS and MARS are concerned then, the competition ladder is more-and-more reflecting the underlying abilities of the teams. 

COLLEY, MASSEY AND ODM

The other Team Rating Systems tracked here on MoS also feel that the competition ladder ordering now represents a reasonable reflection of team abilities. In fact, if anything, they feel there's an even closer match with their own opinions, the various rank correlations for these Systems now being:

  • Colley and the ladder: +0.988
  • ODM and the ladder: +0.969
  • Massey and the ladder: +0.955

Colley ranks only a single team more than two places differently from that team's ladder position: St Kilda, which it ranks 15th and who sit 13th on the ladder.

ODM does the same for four teams:

  • Collingwood (Ranked 5th by ODM and lying 7th on the ladder)
  • Fremantle (3rd and 1st)
  • Hawthorn (1st and 4th)
  • Port Adelaide (10th and 12th)

And, finally, Massey, does the same for five teams:

  • Collingwood (Ranked 5th by Massey and lying 7th on the ladder)
  • Fremantle (3rd and 1st)
  • GWS (10th and 8th)
  • Hawthorn (1st and 4th)
  • Port Adelaide (8th and 12th)

ODM, with nine, was the System re-Ranking most teams this week, while Colley re-Ranked eight and Massey re-Ranked only five. No team was re-Ranked by Colley by more than two places, and Massey re-Ranked only one team by three places (Geelong, down to 12th) as did ODM (GWS, up to 8th).

ODM OFFENSIVE AND DEFENSIVE RANKINGS

ODM's Top 5 Defensive Teams were unchanged by the weekend's results:

  1. Fremantle
  2. Sydney
  3. West Coast
  4. Hawthorn
  5. Richmond

The 115 points that Fremantle gave up to Hawthorn was, I surmise, somewhat discounted by ODM because of the high regard in which it holds the Hawks' Offence.

In fact, the Hawks remain number 1 in an Offensive Top 5 set that look like this:

  1. Hawthorn (no change)
  2. West Coast (no change)
  3. Collingwood (no change)
  4. The Kangaroos (no change)
  5. Adelaide (up from 6th)

The team dropping out of the Top 5 was Geelong, who now sit in 6th.

Seven teams now have ODM Offensive and Defensive Rankings that differ by more than four places:

  • Adelaide (Ranked 11th on Defence, 5th on Offense, and 9th Overall)
  • Essendon (10th, 16th and 14th)
  • Fremantle (1st, 11th and 1st)
  • Geelong (12th, 6th and 11th)
  • The Kangaroos (14th, 4th and 10th)
  • Richmond (5th, 12th and 5th)
  • Sydney (2nd, 8th and 3rd)

Over on the Statistical Analysis blog I introduced a new team rating system, which I called MoSSBOD, based on Scoring Shot Production and Concession. MoSSBOD also produces separate Offensive and Defensive Ratings and Rankings, and the table below compares MoSSBOD's and ODM's opinions.

Overall, the two Systems views are quite similar, the rank correlations being +0.905 for Defensive Rankings, +0.856 for Offensive Rankings, and +0.948 for Combined Rankings.

What most lowers the correlation between the Systems' Offensive Rankings is their differing opinions about the merits of Richmond, which ODM Ranks 12th and MoSSBOD 3rd. ODM is, of course, influenced only by the Tigers' raw points production and by its current assessment of the teams that the Tigers scored those points against.

MoSSBOD differs in two ways: 

  • it considers the Tigers' Scoring Shot production rather than its score (and therefore ignores the fact that the Tigers, at 50.5%, have the competition's third-worst Conversion rate)
  • it assesses each Tigers Scoring Shot performance relative to the quality of the team as assessed at the time the game was played

It's an open question which of the two approaches, ODM's or MoSSBOD's is superior, and one I'll look to address later in the season. Interesting that it makes such a difference for the Tigers at this point in the season though.

PREDICTIVE ACCURACY

ChiPS and MARS remain tied on simple predictive accuracy, both now:

  • 8 tips clear of the Offensive Component of ODM (no change this week)
  • 10 clear of Massey (no change this week)
  • 10 clear of ODM (1 tip further clear this week)
  • 12 clear of the Defensive Component of ODM (1 tip further clear this week)
  • 17 clear of Colley (2 tips further clear this week)