Like the heads-up ending to a Texas Hold 'Em competition it was all mid-table CHiPS action this weekend in the AFL, with positions 4th to 11th all changing hands.

Sydney and Adelaide were the only teams to move by more than a spot, rising two places into 4th and 7th respectively, Sydney's gain of 5.2 Rating Points (RPs) in this round its second-largest in a single game this season, and Adelaide's more modest 1.5 RP gain completing a run of three weeks in which it has accumulated just shy of 10 RPs. Port Adelaide were the only other team to rise during the week, moving up one place into 10th.

Five teams also fell on ChiPS - the Roos, Dockers, Dogs, Pies and Cats - making it eight teams in all that occupied a different spot at round's end than at round's beginning.

(NB: A full version of this table appears at the end of this blog.)

MARS moved nine teams during the week, seven by just a single place, but also the Dogs, which it dropped three places into 10th, and Port Adelaide, which it elevated two places into 8th.

That leaves ChiPS and MARS with no team Ranked more than two places differently, and with a correlation between their Rankings of +0.967 and a correlation between their Ratings of +0.971.

Both Systems now also Rate 10 teams as "above average", Port Adelaide Ranked 10th by ChiPS with a Rating of 1,000.7, and the Western Bulldogs Ranked 10th by MARS with a Rating of 1,007.8 (and over a 10 RP gap to Collingwood in 11th).

COLLEY, MASSEY AND ODM

Colley and ODM both re-Ranked just six teams this week, Colley moving none by more than a single place, but ODM subjecting three teams to multiple-spot moves: Collingwood down to 11th from 8th, Port Adelaide up to 9th from 11th, and the Western Bulldogs down to 6th from 4th.

Massey moved seven teams including three teams by two places, Collingwood from 9th to 11th, Port Adelaide from 11th to 9th, and the Western Bulldogs from 4th to 6th. Those are the same three teams that ODM moved by multiple spots and has resulted in Massey and ODM having identical Team Rankings.

A little less similar are the Rankings of ChiPS and Colley, the correlation of which now stands at +0.936, which is up a little on last week but still the lowest correlation between the Rankings of any pair of Systems. ChiPS also remains least correlated with the competition ladder ordering (+0.942), and Colley the most correlated (+0.998).

Looking across the Systems on a team-by-team basis, only five teams span a range wider than two spots:

• Collingwood, with a high Ranking of 9th on ChiPS, and a low Ranking of 12th on Colley
• Fremantle, with a high Ranking of 1st on Colley, and a low Ranking of 6th on ChiPS
• Hawthorn, with a high Ranking of 1st on ChiPS, MARS, Massey and ODM, and a low Ranking of 4th on Colley
• The Kangaroos, with a high Ranking of 5th on ChiPS, and a low Ranking of 8th on Massey and ODM
• The Western Bulldogs, with a high Ranking of 6th on Colley, Massey and ODM, and a low Ranking of 10th on MARS

As you'd hope after 21 rounds, the Systems are now coming to similar conclusions about the relative merits of the teams' respective seasons.

ODM DEFENSIVE AND OFFENSIVE RANKINGS

ODM is also firming in its opinions about the relative Offensive merits of the 18 teams, with the Top 5 list the same as last week:

1. Hawthorn
2. West Coast
3. Adelaide
4. Kangaroos
5. Western Bulldogs

Port Adelaide remains Ranked 6th, with Geelong moving into 7th and relegating Collingwood to 8th.

There's a little more movement in ODM's Top 5 Defensive teams, but only in their ordering:

1. Fremantle (no change)
2. West Coast (up 1)
3. Sydney (up 1)
4. Hawthorn (down 2)
5. Richmond (no change)

The Western Bulldogs remain Ranked 6th on Defence, while Geelong have also taken 7th place from Collingwood on this ODM ordering.

Six teams are now Ranked five places or more differently on Offence than on Defence according to ODM:

• Adelaide, Ranked 10th on Defence, 3rd on Offence
• Fremantle, 1st and 11th
• The Kangaroos, 12th and 4th
• Port Adelaide, 11th and 6th
• Richmond, 5th and 10th
• Sydney, 3rd and 9th

MoSSBOD's Rankings continue to look similar to ODM's, with Ranking differences exceeding three places only for:

• Richmond's Defence, Ranked 5th by ODM and 1st by MoSSBOD
• Richmond's Offence, Ranked 10th by ODM and 6th by MoSSBOD
• GWS's Defence, Ranked 8th by ODM and 14th by MoSSBOD
• Fremantle's Combined Offence and Defence, Ranked 3rd by ODM and 8th by MoSSBOD

Richmond's climb into first place on MoSSBOD's Defensive Rankings is probably the story of the round for this System, though the elevation of West Coast into first place on the Combined Ranking is also noteworthy.

Currently on MoSSBODs, no team has both a positive Offensive Rating and a negative Defensive Rating, though four have a negative Offensive Rating and a positive Defensive Rating. The remaining 14 teams all have Offensive and Defensive Ratings carrying the same sign, seven with a pair of positive Ratings, and seven more a pair of negative Ratings. 

Correlation between team Offensive and Defensive Ratings now stands at +0.732, which is roughly what it was at the end of Round 20 but up a little on what it had been at the end of earlier rounds (Round 19: +0.707; Round 18: +0.690; Round 17 +0.686; Round 16: +0.578). Whether this trend to higher levels of correlation in Ratings is unique to 2015 or a more general tendency for teams' relative offensive and defensive abilities to move into greater alignment in the latter parts of seasons is something to explore in a future analysis.

PREDICTIVE ACCURACY

MARS gave up a little ground to ChiPS this week allowing ChiPS to establish a one tip lead over it, where a System's tips throughout the season are based solely on whichever team has the higher Rating on that System at the time.

Tipping using only the Offensive Component of the ODM System was also slightly more accurate than using MARS this week, though that method would still have yielded six fewer correct predictions across the course of the entire season.

The remaining methods - using Colley, Massey, ODM or its Defensive Component - all performed equally as well as MARS this week.

FULL ChiPS AND MARS TABLE

Here is the complete, round-by-round ChiPS and MARS table. Please click on it for a version that you might be able to actually read.