In addition to the venerable TCHCR and the RPICH, we offer:
CHODR - The College Hockey Offensive / Defensive Ratings
(pronounced "chowder")
INTRODUCTION
(Those who are impatient may skip to the CHODR ratings at the end).
1. What is CHODR?
CHODR assigns Offensive, Defensive, and an Overall rating to each of
the 44 Division I Men's Ice Hockey teams.
2. How are the ratings determined?
CHODR places equal emphasis on offense and defense and provides an
overall rating for each team based on its offense-defense
combination. A team's Offensive rating is based on the goals it has
scored, with an adjustment for the quality of the defenses it has
faced to score those goals. Similarily, the Defensive rating uses
goals allowed and adjusts for the offensive ratings of the opponents.
The philosophy behind the adjustment calculations is similar to the
least squares optimization that has been used by TCHCR. The Overall
rating is just the difference between a team's Offensive and
Defensive ratings. A more technical explanation of the math will be
available soon for those who are interested.
3. How can the ratings be interpreted?
(a) An offensive/defensive rating represents the goal scoring/
allowing rate (average goals per game) which would be predicted
against a mythical "average" team on neutral ice. An Team with an
Offensive Rating of 6 and a Defensive Rating of 2 would therefore be
predicted to beat an "average" team on neutral ice by the score of 6
to 2.
(b) A positive/negative Overall rating indicates that a team has
more/less overall scoring potential than the "average" team.
(c) We can rank teams according to their overall ratings or provide
separate rankings to reflect offensive or defensive prowess. The
better teams have the higher overall ratings, while the better
offenses have higher offensive ratings and the better defenses have
lower defensive ratings.
4. Comparing individual teams.
One nice feature of this system is that it allows comparisons between
teams on an easily understood numeric basis. Basically, the
difference in overall ratings between two teams represents the
predicted average goal differential if they were to play lots of
games on neutral ice.
Example: Michigan State (0.60 Overall) vs. Alaska-Anchorage (0.10
Overall) would predict an average goal differential of about 0.60 -
0.10 = 0.50 or 1/2 goal in MSU's favor.
5. Predicting future scores.
Another bonus of CHODR is that it may be used to forecast future
scores. The relevant formula is
Team A's predicted goals = A's Offensive Rating
+ B's Defensive Rating
- Average Offensive/Defensive Rating
+/- Home Ice Advantage
Team B's predicted goals = B's Offensive Rating
+ A's Defensive Rating
- Average Offensive/Defensive Rating
+/- Home Ice Advantage
The Average Rating is subtracted from each team's predicted score
because the average is already included in each teams rating, so it
ends up getting included twice when the ratings are summed. The Home
Ice Advantage value gets added to the home team's predicted score and
subtracted from the away team's predicted score. No adjustment is
made for a game on neutral ice. The Home Ice Advantage value used in
the system is +/- 0.375 goals per game, since home teams have, on
average, outscored their opposition by about 0.75 goals per game in
Division I in recent years.
EXAMPLE: Let's try Boston College ( Off = 4.04, Def = 4.16 ) at
Boston University ( Off = 3.52, Def = 2.97 ):
BC's predicted score = ( 4.04 + 2.97 ) - 4.00 - 0.38 = 2.63
BU's predicted score = ( 3.52 + 4.16 ) - 4.00 + 0.38 = 4.06
Although it may seem awkward to predict non-integral scores, this
number actually represents the expected average score for the given
team if they played many games under the given conditions (same
opponent and same location). Of course, in any one game, the actual
result may or may not be close to this average. As we all know,
upsets have been known to occur from time to time.
6. Notes: (sure to generate some controversy)
(a) We do NOT use any information about who wins or loses a game in
generating the ratings. We are intending only to rate a team's
ability to score and keep the other team from scoring. This provides
a direct contrast to TCHCR.
(b) Goals scored in overtime are ignored when generating ratings.
We'd also like to eliminate empty net goals, but getting reliable
data on those is more questionable. Thus our ratings reflect the
regulation time goal scoring ability.
(c) As in TCHCR and RPICH, only games between two Division I teams
are counted. No prior information is used in the rating, i.e. all
teams are equal at the beginning of the season.
(d) Because of the way ratings are calculated, scoring 5 goals
against Maine (Defensive = 2.46) will help your Offensive ratings a
lot more than doing the same to Army (Defensive = 5.97). Likewise,
allowing 6 goals against Maine (Offensive = 6.65) won't hurt your
Defensive ratings as much as allowing the same number to Illinois-
Chicago (Offensive = 2.18). Thus there is an implict strength of
schedule concept here just as in TCHCR.
(e) Like TCHCR, this is just a preliminary look at CHODR. We'd still
like to fiddle with some of the parameters. Also, the estimated
ratings are based on a fairly small number of games so far and will
tend to exhibit considerable variability until later in the season.
Inter-league play will have a large effect on these ratings just as
it does in TCHCR.
(f) We do not intend at all that CHODR should "compete" with TCHCR.
Rather we hope to supply a different perspective to help spark
discussion. The two rating systems complement each other nicely,
since TCHCR concerns itself only with the outcome of the game
(win/loss/tie), while CHODR is concerned only with the score,
regardless of the game outcome.
This rating is a joint effort between both of us. Questions,
comments, and/or suggestions about CHODR are welcomed and encouraged.
Please don't post questions to the list, but mail to us directly. If
possible, please send mail to both of us when inquiring about the
rating.
Timothy J. Danehy [log in to unmask]
Robin Lock [log in to unmask]
Without further ado ....
CHODR - The College Hockey Offensive / Defensive Ratings
(based on games through 12/05/92)
Division I Offense Defense Overall
Rank Team Record Rating Rank Rating Rank Rating
------------------------------------------------------------------------------
1 Maine 11 0 1 6.652 1 2.464 1 4.188
2 Clarkson 5 4 1 4.900 2 2.925 5 1.975
3 Michigan 8 3 2 4.356 14 2.759 2 1.597
4 Wisconsin 8 5 1 4.323 15 2.836 3 1.487
5 Miami 10 3 1 4.816 4 3.509 13 1.307
6 Lake Superior 7 1 3 4.574 6 3.381 10 1.193
7 St Lawrence 7 2 1 4.425 12 3.495 12 0.930
8 St Cloud 7 5 0 4.480 9 3.563 14 0.917
9 Minnesota-Duluth 8 3 1 4.740 5 3.837 19 0.903
10 Denver 7 4 1 4.556 7 3.855 20 0.702
11 Harvard 7 1 1 4.148 19 3.460 11 0.687
12 Minnesota 5 3 4 4.435 11 3.807 18 0.627
13 UMass-Lowell 9 4 0 3.843 25 3.225 8 0.618
14 Michigan State 7 4 1 4.183 17 3.583 15 0.600
15 Yale 4 4 1 4.524 8 3.966 21 0.558
16 Michigan Tech 5 8 1 4.167 18 3.614 17 0.553
17 Boston University 5 4 1 3.520 31 2.968 6 0.552
18 RPI 5 2 2 3.300 35 2.914 4 0.386
19 Providence 5 7 1 4.231 16 4.028 23 0.203
20 New Hampshire 5 5 2 4.383 13 4.274 29 0.109
21 Alaska-Anchorage 5 1 0 3.254 36 3.154 7 0.100
22 Alaska-Fairbanks 6 3 0 3.588 30 3.604 16 -0.016
23 Bowling Green 6 9 0 4.007 22 4.086 25 -0.079
24 Boston College 4 5 3 4.040 21 4.158 26 -0.118
25 Western Michigan 8 4 1 3.819 27 4.043 24 -0.224
26 North Dakota 4 10 0 4.446 10 4.749 35 -0.304
27 Colorado College 3 10 0 3.966 23 4.297 30 -0.331
28 Brown 4 5 0 4.045 20 4.398 33 -0.353
29 Vermont 5 4 1 2.873 40 3.340 9 -0.467
30 Northern Michigan 5 7 2 3.827 26 4.391 32 -0.564
31 Kent 4 7 1 3.741 28 4.339 31 -0.598
32 Northeastern 6 5 0 4.827 3 5.457 41 -0.630
33 Princeton 3 4 0 3.389 33 4.524 34 -1.135
34 Ferris State 3 5 2 3.073 39 4.219 27 -1.146
35 Notre Dame 1 11 1 3.419 32 4.982 37 -1.563
36 Cornell 2 4 1 2.306 43 4.007 22 -1.701
37 Merrimack 3 8 1 3.855 24 5.687 43 -1.832
38 Colgate 0 8 0 3.362 34 5.365 40 -2.003
39 Union 1 6 0 2.744 41 4.752 36 -2.008
40 Illinois-Chicago 2 9 1 2.175 44 4.240 28 -2.065
41 Ohio State 3 8 1 3.115 38 5.294 39 -2.179
42 Army 1 1 0 3.590 29 5.972 44 -2.382
43 Air Force 1 5 1 3.131 37 5.595 42 -2.464
44 Dartmouth 1 5 0 2.326 42 5.177 38 -2.850
------------------------------------------------------------------------------
Average Team: 4.000 4.000 0.000
------------------------------------------------------------------------------
Home Ice Advantage = +/- 0.375 Goals Per Game.
------------------------------------------------------------------------------
Based on 237 Division I games.
Notes for 12/7/92:
Since this is the inaugural edition of CHODR, we don't have much to
talk about in terms of movement in the rating.
It shouldn't come as a surprise to most (or any) of you who ends up
in the top spot here as in the other ratings. Note the large gap
between the #1 offense of Maine and #2 Clarkson. Note also that
Maine's combo of #1 offense and #1 defense gives them an incredible
margin of 2.2 over the runner-up in the overall rating.
The award for lopsidedness (good offense and bad defense or
vice-versa) is no contest this week as the Northeastern Huskies boast
the #3 ranked offense but are way down at #41 on defense. On the
other side, RPI is #35 offense and #4 defense while Vermont is #40
offense and #9 defense.
The 4.000 offensive/defensive rating for the average team means that
the average score per team per game in the 237 Division I games
played so far has been exactly 4.
Timothy J. Danehy [log in to unmask]
Robin Lock [log in to unmask]
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