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# Pro Football Reference Blog

## NCAA: SRS ratings through seven weeks

Posted by Chase Stuart on October 17, 2010

Regular PFR readers will recall that we published college football SRS ratings every week last season. With seven weeks in the books, and the BCS opening rankings coming out tonight, it made sense to start up the project for 2010. So how do we come up with SRS grades for college football teams?

PFR has used the Simple Rating System to grade college and NFL teams for years. All ratings or rankings are meaningless without explanation, and the link above explains what the SRS tries to do. The SRS version that I'm implementing below is most useful to predict future results; the SRS is predictive, not retrodictive. That means the SRS will have no trouble at all ranking a team that's undefeated and beat a team with one loss behind the very team it beat. Why? One, because we know that one game is just one game, and never is conclusive proof that one team is better than another; and two, because the SRS weighs each game equally. Of course, sample size issues are always present here; while I've waited for seven weeks before presenting the SRS, we really need to see a couple more weeks of action before we can have full faith in this system. For now, though, maybe they'll make you rethink your perception of a couple of teams.

So how am I calculating these simple ratings?

1) For each game, 3 points are given to the road team (unless it's a neutral site game). After that adjustment, all wins and losses of between 7 and 24 points are scored as however many points the team won by. So a 24-10 road win goes down as +17 for the road team, -17 for the home team.

2) Wins of 7 or fewer points are scored as 7-point wins and losses of 7 or fewer points are scored as 7 point losses, except that road losses of 3 or fewer and home wins of 3 or fewer are graded as 0 point ties. So a 21-20 home victory goes down as a tie for both teams. This is not as drastic as it sounds, because the SRS ultimately is not concerned with win/loss records. There is no distinction between a win and a loss (you don't need to make such distinctions in predictive systems) except for when the game is close. So three 10-point wins scores +30, just as two 20-point wins and a 10-point loss scores as +30. However, three 3 point wins (+9 before the adjustments, +21 after) is worth more than two 10 point wins and a 1 point home loss (+21 before, +13 after).

3) Wins/Losses of more than 24 points are scored as the average between the actual number and 24. This is to avoid giving undue credit to teams that run up the score. Oregon bludgeoned New Mexico on opening day, 72-0, but that "only" goes down as a 46.5 point win. Why? Because the game was in Eugene (dropping it to +69) and the average of 24 and 69 is 46.5. However, in FCS/I-AA games, there is no run-up-the-score modifier. Why? Otherwise, the elite teams could beat the FCS cupcakes by 64 points and go down in this system. Major thanks to Peter R. Wolfe for providing the game scores.

Doug (and the readers) might argue that I've taken the first "S" out of the SRS, but I think these ratings are still simple. They're merely designed to get an approximate rating on how strong each team really is. By using just points scored and points allowed, we're obviously leaving lots of information behind. That's why I still think these are pretty simple, but a large improvement over looking at just points differential or won/loss records.

After translating the raw scoring differential using the system above to a "SRS" victory margin, I simply add the victory margin for each game to the strength of schedule for the opponent. A 24-point win over an average team is equivalent to a 14-point win over a team that's 10 points better than average. I ran hundreds of iterations to figure out the true strength of schedule for each opponent and the true rating for each team; this involves adjusting the SOS of each team's opponents by the SOS of those opponents, and so on. Don't worry: at the end, the results converge, and we have true and legitimate ratings. My favorite part about the SRS is that everything adds up at the end. So after posting the ratings for each team, you could go through the schedule of any of the 120 FBS teams and understand exactly why their rating was what it was. I'll do that below with the top five teams. First, the results:

1 Oregon 6 33.1 38.7 71.7 6-0 P10 1 61
2 Stanford 6 17.1 48.1 65.2 5-1 P10 2 8
3 TCU 7 27.6 37.5 65.1 7-0 MWC 1 69
4 Boise St 6 26.9 36.9 63.9 6-0 WAC 1 73
5 Missouri 6 21.3 42.0 63.2 6-0 B12 1 34
6 Oklahoma 6 14.0 46.7 60.7 6-0 B12 2 13
7 Alabama 7 16.7 42.1 58.8 6-1 SEC 1 33
8 Nebraska 6 18.5 39.9 58.4 5-1 B12 3 48
9 Ohio State 7 18.9 38.8 57.7 6-1 B10 1 59
10 Utah 6 25.9 31.7 57.6 6-0 MWC 2 105
11 Arizona St 6 9.8 47.7 57.5 3-3 P10 3 10
12 Southern Cal 7 11.6 45.7 57.2 5-2 P10 4 19
13 Florida St 7 18.4 38.7 57.1 6-1 ACC 1 60
14 Oklahoma St 6 18.3 38.3 56.7 6-0 B12 4 63
15 Arizona 6 16.0 40.4 56.4 5-1 P10 5 43
16 California 6 9.7 46.6 56.3 3-3 P10 6 14
17 Auburn 7 14.0 42.2 56.2 7-0 SEC 2 30
18 Michigan St 7 16.1 39.6 55.8 7-0 B10 2 53
19 Nevada 7 17.6 37.7 55.3 6-1 WAC 2 66
20 South Carolina 6 8.8 46.2 55.0 4-2 SEC 3 16
21 LSU 7 12.1 42.2 54.2 7-0 SEC 4 31
22 Oregon St 6 -0.8 54.9 54.1 3-3 P10 7 1
23 Wisconsin 7 16.4 37.4 53.8 6-1 B10 3 70
24 Virginia Tech 7 13.0 40.5 53.5 5-2 ACC 2 42
25 Iowa 6 18.1 35.3 53.4 5-1 B10 4 88
26 Texas A&M 6 6.8 46.3 53.1 3-3 B12 5 15
27 Florida 7 6.9 45.5 52.4 4-3 SEC 5 20
28 Georgia 7 9.1 43.3 52.4 3-4 SEC 6 23
30 Arkansas 6 8.8 42.6 51.4 4-2 SEC 7 27
29 Hawai`i 7 11.5 39.9 51.4 5-2 WAC 3 46
31 Miami FL 6 10.5 40.7 51.2 4-2 ACC 3 41
32 Air Force 7 13.4 37.6 51.1 5-2 MWC 3 67
33 North Carolina 6 8.4 42.4 50.8 4-2 ACC 4 29
34 Mississippi St 7 10.9 39.9 50.8 5-2 SEC 8 50
35 North Carolina St 7 11.3 39.4 50.7 5-2 ACC 5 57
36 Illinois 6 3.0 47.5 50.5 3-3 B10 5 11
37 Texas 6 5.8 44.5 50.2 4-2 B12 6 21
38 San Diego St 6 15.8 34.1 49.8 4-2 MWC 4 92
39 Cincinnati 6 7.8 41.9 49.7 3-3 BigE 1 35
40 Notre Dame 7 3.6 46.1 49.6 4-3 INDY -- 18
41 Pittsburgh 6 6.3 42.7 49.0 3-3 BigE 2 26
42 Kansas St 6 8.4 40.4 48.8 5-1 B12 7 44
43 Baylor 7 11.6 36.8 48.3 5-2 B12 8 78
44 Central Florida 6 13.3 34.6 47.9 4-2 CUSA 1 91
45 UCLA 6 -2.0 48.4 46.4 3-3 P10 8 7
46 Michigan 7 5.1 41.2 46.3 5-2 B10 6 40
49 Colorado 6 -4.8 50.8 46.0 3-3 B12 9 4
48 West Virginia 6 13.3 32.7 46.0 5-1 BigE 3 97
47 Washington 6 -4.3 50.4 46.0 3-3 P10 9 6
50 Clemson 6 9.7 35.0 44.6 3-3 ACC 6 90
51 Idaho 6 9.5 35.0 44.5 3-3 WAC 4 89
53 Connecticut 6 10.8 32.4 43.3 3-3 BigE 4 99
52 Kentucky 7 3.6 39.6 43.3 4-3 SEC 9 51
54 Georgia Tech 7 8.2 33.9 42.1 5-2 ACC 7 93
55 Navy 6 3.3 38.4 41.7 4-2 INDY -- 62
56 Texas Tech 6 0.2 41.4 41.6 3-3 B12 10 39
57 Penn State 6 -0.7 42.1 41.5 3-3 B10 7 32
58 Northern Illinois 7 9.2 32.2 41.4 5-2 MAC 1 101
59 Northwestern 6 10.8 30.5 41.3 5-1 B10 8 114
60 SMU 7 1.3 39.6 40.9 4-3 CUSA 2 55
61 Tulsa 7 9.1 31.7 40.8 4-3 CUSA 3 104
62 Fresno St 6 5.1 35.4 40.5 4-2 WAC 5 86
63 Louisville 6 5.1 35.4 40.4 3-3 BigE 5 87
64 East Carolina 6 -1.3 41.8 40.4 4-2 CUSA 4 36
65 Tennessee 6 -4.2 44.4 40.3 2-4 SEC 10 22
66 Iowa St 7 -7.6 47.3 39.7 3-4 B12 11 12
67 Maryland 6 8.2 31.1 39.3 4-2 ACC 8 107
68 Mississippi 6 1.2 37.8 39.0 3-3 SEC 11 65
69 Brigham Young 7 -12.2 51.0 38.8 2-5 MWC 5 3
70 Troy 6 7.0 31.4 38.4 4-2 SunB 1 106
71 Purdue 6 1.3 36.9 38.2 4-2 B10 9 76
72 Toledo 7 -3.3 41.5 38.2 4-3 MAC 2 37
74 Southern Miss 7 8.3 29.6 37.9 5-2 CUSA 5 116
73 Temple 7 1.0 36.9 37.9 5-2 MAC 3 75
75 Houston 6 6.4 30.5 37.0 3-3 CUSA 6 112
77 Rutgers 6 4.8 32.0 36.8 4-2 BigE 6 102
76 Ohio U. 7 6.1 30.7 36.8 4-3 MAC 4 109
78 South Florida 6 6.1 30.6 36.7 3-3 BigE 7 111
80 Army 7 6.0 30.5 36.5 4-3 INDY -- 113
79 Vanderbilt 6 -5.0 41.5 36.5 2-4 SEC 12 38
81 Syracuse 6 6.6 29.6 36.2 4-2 BigE 8 117
82 Virginia 6 -1.1 37.2 36.1 2-4 ACC 9 71
83 Louisiana Tech 7 -4.1 39.9 35.8 3-4 WAC 6 47
84 Boston College 6 -8.2 43.3 35.2 2-4 ACC 10 24
85 Miami OH 7 -5.4 39.6 34.2 4-3 MAC 5 52
86 Wyoming 7 -16.4 50.4 34.1 2-5 MWC 6 5
87 Indiana 6 4.8 29.1 33.8 4-2 B10 10 118
88 Florida Int'l 6 -2.9 36.4 33.4 2-4 SunB 2 81
89 Colorado St 7 -13.0 46.1 33.1 2-5 MWC 7 17
90 Western Michigan 6 -3.5 36.3 32.8 2-4 MAC 6 83
91 Washington St 7 -18.9 51.7 32.8 1-6 P10 10 2
92 Utah St 6 -6.6 38.9 32.3 2-4 WAC 7 58
93 Wake Forest 7 -7.8 40.0 32.2 2-5 ACC 11 45
94 Minnesota 7 -7.7 39.6 31.9 1-6 B10 11 56
95 Central Michigan 7 1.1 30.7 31.8 2-5 MAC 7 110
96 Alabama-Birmingham 6 -6.8 36.5 29.7 2-4 CUSA 7 79
97 Arkansas St 7 -4.4 33.3 28.9 2-5 SunB 3 95
98 Kent St 6 -2.0 30.5 28.5 2-4 MAC 8 115
99 Bowling Green 7 -8.2 36.4 28.2 1-6 MAC 9 80
100 Buffalo 6 -8.9 37.1 28.2 2-4 MAC 10 72
101 San José St 7 -19.8 47.8 28.0 1-6 WAC 8 9
102 Duke 6 -12.7 39.9 27.2 1-5 ACC 12 49
103 Marshall 6 -15.9 42.4 26.5 1-5 CUSA 8 28
105 UTEP 7 6.4 20.1 26.5 5-2 CUSA 9 120
104 UNLV 7 -16.8 43.3 26.5 1-6 MWC 8 25
106 Rice 7 -12.0 37.6 25.6 2-5 CUSA 10 68
107 Florida Atlantic 5 -7.5 32.6 25.1 1-4 SunB 4 98
108 Kansas 6 -11.5 36.1 24.6 2-4 B12 12 85
109 Ball St 7 -7.4 31.8 24.3 2-5 MAC 11 103
110 Louisiana-Lafayette 6 -12.8 36.2 23.4 2-4 SunB 5 84
111 Tulane 6 -11.4 33.6 22.2 2-4 CUSA 11 94
112 Middle Tennessee St 6 -4.4 26.1 21.7 2-4 SunB 6 119
113 Louisiana-Monroe 6 -10.7 32.4 21.7 3-3 SunB 7 100
114 Western Kentucky 6 -17.0 37.9 20.9 0-6 SunB 8 64
115 North Texas 7 -11.9 31.1 19.2 1-6 SunB 9 108
116 Eastern Michigan 7 -18.0 36.8 18.8 1-6 MAC 12 77
117 Memphis 7 -20.1 36.9 16.9 1-6 CUSA 12 74
118 New Mexico St 6 -22.6 36.3 13.7 1-5 WAC 9 82
119 Akron 7 -19.4 32.9 13.6 0-7 MAC 13 96
120 New Mexico 6 -26.8 39.6 12.8 0-6 MWC 9 54
P10 54.4
B12 49.3
SEC 49.2
B10 45.8
ACC 43.3
BigE 42.3
MWC 41.0
WAC 40.6
CUSA 32.7
MAC 30.4
SunB 25.8

So how do Oregon, Stanford, TCU, Boise State and -- Missouri come out on top?

18-Sep-10 Oregon 69 Portland St 0 Home 66 23.4 89.4
2-Oct-10 Oregon 52 Stanford 31 Home 18 65.2 83.2
25-Sep-10 Oregon 42 Arizona St 31 Road 14 57.5 71.5
11-Sep-10 Oregon 48 Tennessee 13 Road 31 40.3 71.3
4-Sep-10 Oregon 72 New Mexico 0 Home 46.5 12.8 59.3
9-Oct-10 Oregon 43 Washington St 23 Road 23 32.8 55.8

Oregon put their foot on the throats of Portland State, New Mexico and Tennessee, and outlasted Stanford and Arizona. Their 20 point win against Washington State (which fell far short of covering the spread) was their worst performance of the season so far.

11-Sep-10 Stanford 35 UCLA 0 Road 31 46.4 77.4
25-Sep-10 Stanford 37 Notre Dame 14 Road 25 49.6 74.6
18-Sep-10 Stanford 68 Wake Forest 24 Home 32.5 32.2 64.7
4-Sep-10 Stanford 52 Sacramento St 17 Home 32 31.4 63.4
9-Oct-10 Stanford 37 Southern Cal 35 Home 0 57.2 57.2
2-Oct-10 Stanford 31 Oregon 52 Road -18 71.7 53.7

Stanford gets penalized for losing to Oregon, but that was their worst game of the year. Blowout wins over respectable UCLA and Notre Dame teams were impressive, and Stanford has looked good for 5.5 games so far.

18-Sep-10 TCU 45 Baylor 10 Home 28 48.3 76.3
9-Oct-10 TCU 45 Wyoming 0 Home 33 34.1 67.1
11-Sep-10 TCU 62 Tennessee Tech 7 Home 52 13.1 65.1
16-Oct-10 TCU 31 Brigham Young 3 Home 24.5 38.7 63.2
4-Sep-10 TCU 30 Oregon St 21 Arlington TX 9 54.1 63.1
24-Sep-10 TCU 41 SMU 24 Road 20 40.9 60.9

No one has been as consistent as TCU: Their worst game of the year was a 27-0 win in Fort Collins. They beat Oregon State, the best team they faced, and blew out Baylor, the only other legitimate team they've faced so far. But TCU is most impressive for their consistent dominance. They've allowed just three points in three games in October.

9-Oct-10 Boise St 57 Toledo 14 Home 32 38.2 70.2
18-Sep-10 Boise St 51 Wyoming 6 Road 36 34.1 70.1
16-Oct-10 Boise St 48 San José St 0 Road 37.5 28.0 65.5
25-Sep-10 Boise St 37 Oregon St 24 Home 10 54.1 64.1
2-Oct-10 Boise St 59 New Mexico St 0 Road 43 13.7 56.7
6-Sep-10 Boise St 33 Virginia Tech 30 Landover MD 3 53.5 56.5

That huge victory over Virginia Tech on opening night? That's the least impressive game for the Broncos this year, according to the SRS. Boise State has won by 40+ in four other games, and handled Oregon State much easier than the 13-point margin would have you think.

16-Oct-10 Missouri 30 Texas A&M 9 Road 24 53.1 77.1
9-Oct-10 Missouri 26 Colorado 0 Home 23 46.0 69.0
25-Sep-10 Missouri 51 Miami OH 13 Home 29.5 34.2 63.7
4-Sep-10 Missouri 23 Illinois 13 St Louis MO 10 50.5 60.5
11-Sep-10 Missouri 50 McNeese St 6 Home 41 18.3 59.3
18-Sep-10 Missouri 27 San Diego St 24 Home 0 49.8 49.8

Missouri's two best games came the last two weeks. They've played an easy schedule, but dominated the Aggies in College Station this past Saturday. The win over Illinois looks better now that the Illini won in State College and were competitive against the Buckeyes. Missouri surprisingly comes in fifth in this modified margin of victory category, thanks to ranking second in college football in points allowed. The Tigers haven't had a difficult schedule, but it hasn't been full of cupcakes, either. I wouldn't book my Fiesta Bowl tickets just yet if I was Jason -- squeaking by San Diego State isn't a very good sign but Missouri seems to be underrated so far by the national media. The Sooners come to Columbia this weekend (as does Gameday), so we'll get an answer on how good Missouri is very soon.

This entry was posted on Sunday, October 17th, 2010 at 7:56 pm and is filed under BCS, College. You can follow any responses to this entry through the RSS 2.0 feed. Both comments and pings are currently closed.