2015 College Football Ratings – Week 2 and Primer

This is the ninety-seventh year in which I’ve messed around with some sort of college football rating schema – lots of changes, different viewpoints, etc – and I think we’re finally onto something.  Last year I used drive success rates, which was helpful – but frankly a lot of work, and at the end of the day somewhat questionable in its utility.  I am not sure we got to a better answer, although the top of last year’s charts were absolutely justifiable.  Of course, what system is not justifiable?  But this year, I’m doing something simpler – rigorous, but focusing on final scores.  At the end of the day we have two dimensions to look at – who did you beat, and how did you play.  Ultimately, what matters is who you beat (and lose to), so I was looking for a way to not lose that data, while still focusing on the wins.  What we do here instead is to use the margin of victory – the best indicator of a team’s actual quality – to determine schedule strength. (instead of opponents winning percentage, focus on opponents margin of victory)  Then use that schedule strength to normalize wins and losses.  How does it work?

  1. Schedule strength
    1. We look at the margin of victory in every game, using a diminishing return scale.  Every point up to 28 points counts (so a 28 point win is worth 14 points more than a 14 point win).  After 28 points, each additional point counts a half. (so a 35 point win is worth 28 + .5*7 = 31.5 points).  After 42 points, each additional point counts one tenth.  So Boston College’s 72-0 win over Howard is only worth (28 + 14*0.5 + 30*0.1) 38 points.
    2. In the case of true road games, a road added is given to the road team.  This adder is equal to the aggregate margin of victory between true home and away teams in FBS games.  Last year it ended up at 3.3 points.  Right now, it’s at 7.1 points (it will shrink).
    3. Calculating margin of victory and opponents margin of victory (in games not involving your team) is pretty straightforward from here.  However, we know that in reality your opponents’ opponents scoring margin should impact your opponents strength too.  Of course you can go on and on like this (a mathematical wormhole).  Last year after 10 iterations, the standard deviation across teams got down to basically zero. (a point where adding more iterations did not give any more information)  Of course right now, the 10th iteration is not too helpful, so we go to 20 iterations.  The standard deviation will shrink over the season of course.
    4. We take the collected result (your margin relative to opponents margin relative to their opponents margin relative to … and so on) and scale it from 0 to 1.  This scale number is the strength of the team.
  2. Relating it to wins
    1. Now that the opponents have “value”, how much is beating a team worth.  If a team has a rating of t, a win is worth t and a loss is worth minus (1-t).  So the top scoring margin right now is Alabama.  So a win over Bama is worth 1 full point and a loss has no deduction.  A win over a team with a .95 rating is worth 0.95 points, while a loss deducts 0.05 points and so on.
    2. In theory we could do a W/L percentage here, but the problem is that it treats all unbeatens equally, which tells us nothing about relative quality of resume.  So we take the “win points” subtract the “loss points” and scale it to a per game basis.  We also give extra credit and blame for true road wins and home losses (based on collective win/loss in true home-road games between FBS teams).
    3. All non-FBS teams are treated as “Other” in order to fairly capture their impact on schedule.  Other measures like RPI disregard those games, but they are too big a portion of many college schedules to just set aside like you might for basketball.

Now the results below are preliminary – so little is known about true schedule quality.  Also, not everybody has played 2 games, which would allow strength of schedule metrics to be mathematically correct.  In particular pay attention to the “scale”.  A lot of teams are bunched up between #16 and #42, so the relative ranking there is pretty meaningless.  (as if the others are that helpful)

W L Pts Scale
1 LSU 1 0 0.9967 1.000
2 Notre Dame 2 0 0.8696 0.929
3 UCLA 2 0 0.7640 0.871
4 Ohio State 2 0 0.7303 0.852
5 BYU 2 0 0.7259 0.850
6 Alabama 2 0 0.6819 0.825
7 Oklahoma 2 0 0.6765 0.822
8 Georgia 2 0 0.6615 0.814
9 Western Kentucky 2 0 0.6609 0.814
10 Temple 2 0 0.6505 0.808
11 Ohio 2 0 0.5854 0.772
12 Kentucky 2 0 0.5601 0.758
13 Tulsa 2 0 0.5168 0.734
14 Florida State 2 0 0.4960 0.722
15 TCU 2 0 0.4920 0.720
16 Miami-FL 2 0 0.4720 0.709
17 USC 2 0 0.4449 0.694
18 Missouri 2 0 0.4244 0.682
19 Utah 2 0 0.4110 0.675
20 Kansas State 2 0 0.3866 0.661
21 Arizona 2 0 0.3742 0.655
22 Texas A&M 2 0 0.3734 0.654
23 Northern Illinois 2 0 0.3728 0.654
24 Pittsburgh 2 0 0.3655 0.650
25 Oklahoma State 2 0 0.3478 0.640
26 Iowa 2 0 0.3359 0.633
27 Syracuse 2 0 0.3245 0.627
28 Houston 2 0 0.3218 0.626
29 Old Dominion 2 0 0.3215 0.625
30 Air Force 2 0 0.3205 0.625
31 Clemson 2 0 0.3079 0.618
32 California 2 0 0.3054 0.616
33 Northwestern 2 0 0.3032 0.615
34 Illinois 2 0 0.2925 0.609
35 Duke 2 0 0.2921 0.609
36 NC State 2 0 0.2918 0.609
37 Auburn 2 0 0.2909 0.608
38 Hawaii 1 1 0.2901 0.608
39 Mississippi State 1 1 0.2844 0.605
40 Charlotte 2 0 0.2823 0.604
41 Ole Miss 2 0 0.2794 0.602
42 Memphis 2 0 0.2784 0.601
43 Florida 2 0 0.2556 0.589
44 Baylor 2 0 0.2506 0.586
45 Georgia Tech 2 0 0.2391 0.580
46 Boston College 2 0 0.2311 0.575
47 Navy 1 0 0.2311 0.575
48 Toledo 1 0 0.2280 0.573
49 Connecticut 2 0 0.2201 0.569
50 West Virginia 2 0 0.2124 0.565
51 Indiana 2 0 0.1936 0.554
52 Tennessee 1 1 0.1881 0.551
53 Texas 1 1 0.1864 0.550
54 Wisconsin 1 1 0.1759 0.545
55 Boise State 1 1 0.1650 0.538
56 Michigan State 2 0 0.1531 0.532
57 Bowling Green 1 1 0.1406 0.525
58 Penn State 1 1 0.1397 0.524
59 Texas Tech 2 0 0.1227 0.515
60 Colorado 1 1 0.1209 0.514
61 MTSU 1 1 0.1155 0.511
62 Virginia Tech 1 1 0.1122 0.509
63 LA-Monroe 1 1 0.0755 0.489
64 South Florida 1 1 0.0737 0.488
65 Texas State 1 1 0.0737 0.488
66 Minnesota 1 1 0.0574 0.479
67 Nebraska 1 1 0.0469 0.473
68 Miami-OH 1 1 0.0445 0.472
69 Marshall 1 1 0.0363 0.467
70 South Carolina 1 1 0.0276 0.462
71 Southern Miss 1 1 0.0256 0.461
72 Cincinnati 1 1 0.0114 0.453
73 Washington 1 1 0.0076 0.451
74 Rice 1 1 0.0069 0.451
75 South Alabama 1 1 -0.0008 0.446
76 Buffalo 1 1 -0.0027 0.445
77 Louisiana Tech 1 1 -0.0091 0.442
78 Michigan 1 1 -0.0208 0.435
79 Ball State 1 1 -0.0329 0.429
80 LA-Lafayette 1 1 -0.0344 0.428
81 Purdue 1 1 -0.0377 0.426
82 Kent State 1 1 -0.0443 0.422
83 Appalachian State 1 1 -0.0459 0.421
84 San Diego State 1 1 -0.0486 0.420
85 Virginia 0 2 -0.0492 0.420
86 Oregon State 1 1 -0.0508 0.419
87 Fresno State 1 1 -0.0521 0.418
88 Utah State 1 1 -0.0586 0.414
89 Troy 1 1 -0.0632 0.412
90 Arizona State 1 1 -0.0647 0.411
91 Wake Forest 1 1 -0.0649 0.411
92 San Jose State 1 1 -0.0716 0.407
93 North Carolina 1 1 -0.0892 0.397
94 Colorado State 1 1 -0.0963 0.394
95 New Mexico 1 1 -0.1003 0.391
96 East Carolina 1 1 -0.1025 0.390
97 Maryland 1 1 -0.1154 0.383
98 Stanford 1 1 -0.1283 0.376
99 Nevada 1 1 -0.1768 0.349
100 FIU 1 1 -0.1908 0.341
101 Central Michigan 1 1 -0.1915 0.341
102 Oregon 1 1 -0.1917 0.341
103 Iowa State 1 1 -0.1992 0.336
104 Washington State 1 1 -0.2050 0.333
105 Georgia Southern 1 1 -0.2059 0.333
106 Vanderbilt 0 2 -0.2352 0.316
107 Massachusetts 0 1 -0.2387 0.314
108 Georgia State 1 1 -0.2490 0.309
109 UNLV 0 2 -0.2549 0.306
110 Rutgers 1 1 -0.2570 0.304
111 Eastern Michigan 1 1 -0.2573 0.304
112 SMU 1 1 -0.3014 0.280
113 Idaho 0 2 -0.3286 0.265
114 Arkansas 1 1 -0.3580 0.248
115 Florida Atlantic 0 2 -0.3612 0.247
116 Other 4 67 -0.3933 0.229
117 Akron 0 2 -0.4329 0.207
118 Arkansas State 0 2 -0.4340 0.206
119 UTSA 0 2 -0.4629 0.190
120 Tulane 0 2 -0.5348 0.150
121 North Texas 0 1 -0.6345 0.095
122 UTEP 0 2 -0.6374 0.093
123 New Mexico State 0 2 -0.6395 0.092
124 Louisville 0 2 -0.6933 0.062
125 UCF 0 2 -0.7009 0.058
126 Kansas 0 2 -0.7178 0.049
127 Army 0 2 -0.7244 0.045
128 Western Michigan 0 2 -0.7537 0.029
129 Wyoming 0 2 -0.8054 0.000
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