[Ed. Note: This is the first post by my good friend and stat guru Chase Stuart. For at least the rest of this season, Chase will be contributing his unique perspective to the site. Chase has previously contributed to the New York Times Fifth Down and the Pro-Football Reference Blog. You can also follow Chase on twitter.]

The last two seasons, I have published college football ratings using the Simple Rating System. Before explaining how the Simple Rating System (SRS) works, allow me to first explain what the SRS is trying to do (and just as importantly, what it’s not trying to do).

Most rating systems fall into one of two categories. A rating system could simply replicate the standings in any particular league; such a rating system would best be described as retrodoctive or explanatory. A retrodictive rating system fits the data to explain what happened in the past. The BCS computer ratings are mostly retrodictive; so are player or team ratings that give significant weight to high-leverage plays that tend to be highly random (clutch play, fumble recovery rates, etc.). An explanatory rating system tries to measure how much a team or player has accomplished in the past; it does not attempt to answer the question “what will happen next?” When Bill Parcells said “You are what your record says you are,” he’s championing retrodictive ratings. So was Rich Kotite when, coaching the 7-2 Eagles in 1994, he said to the media: “Judge me by my record.” An explanatory rating system would say that Kotite and his Eagles were doing well; but it would never have predicted that Kotite would go 4-35 over the next — and final — 39 games of his career.

The other type of rating system is a predictive system, which works as they name implies: it tries to predict the future. Here is a useful chart detailing some of the differences between the two in college football rating systems. Predictive rating systems are not very concerned with wins and losses; instead, they focus on more granular pieces of data. The best and most obvious example of a predictive rating system would be the formulas used by the folks in Vegas. Those who make point spreads aren’t disturbed if their rankings place Team A, which has “accomplished less” than Team B, higher up in their rankings. This weekend produced a useful example. No purely retrodictive rating system would put the Oklahoma Sooners ahead of the Kansas State Wildcats. Oklahoma was 6-1 but lost to a mediocre Texas Tech team; Kansas State was undefeated and had beaten some solid teams, albeit in less than thrilling fashion. Both the BCS ratings and the Associated Press’ rankings had Kansas State over Oklahoma, because those systems are designed to acknowledge accomplishments. But despite being the higher ranked team and playing at home, Kansas State was a 14-point underdog to the Sooners. And Oklahoma promptly went into Manhattan and blew out the Wildcats, 58-17.

The SRS is a predictive system, which means it could theoretically place a 3-5 team ahead of a 7-1 team. As a sanity check, it usually tends to correlate pretty well with the point spread in most games (and it’s worth trying to understand the deviation when the lines do not match up). But as the name implies, it’s simple. The SRS does not factor in the thousands of pieces of data one could place into a rating system, trading precision for elegance and ease of understanding. Here’s how it works:

The SRS takes only two factors into account: strength of schedule and adjusted margin of victory. Each game is given equal weight. Therefore, the sum of a team’s SOS and MOV rating is its SRS rating. A team could have an SRS rating of 60 by having an MOV of 30 and an SOS of 30, or an MOV rating of 40 and an SOS of 40. Once you have the SRS scores for each team, it’s very simple to understand how the system arrived at those ratings. Further, the numbers the system spits out are easy to understand: if Team A has a rating of 55 and Team B has a rating of 44, it means that Team A is predicted to be 11 points better than Team B. The units here mean exactly what you think they mean.

It’s complicated to create these ratings, but I’ve done that in Excel for you. The tricky part is that each team’s strength of schedule is dependent on the ratings of each of their opponents, which is dependent on the ratings of each of their opponents, which includes the original team we’re trying to rate. If you adjust each team’s rating over hundreds of thousands of iterations, eventually the ratings converge, and we’re left with “true” ratings.

One last note: I wrote about that the SRS uses adjusted margin of victory. What does that mean? For starters, the road team is given 3 points for each game (but there is no home or road team for neutral site games). After that adjustment, all wins and losses of between 7 and 24 points as exactly that. So a 24-10 road win goes down as +17 for the road team, -17 for the home team. 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/home wins of 3 or fewer are graded as 0 point ties). This gives a very minor boost to teams that win by a couple of points. Finally, wins of more than 24 points/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.

Now, the college football SRS ratings after week 9:

Rk Team Con G MOV SOS SRS W-L 1. LSU SEC 8 24.5 43.9 68.4 8-0 2. Alabama SEC 8 27.4 40.7 68.1 8-0 3. Oklahoma St B12 8 22.0 45.2 67.2 8-0 4. Stanford P12 8 27.4 39.2 66.5 8-0 5. Oklahoma B12 8 21.5 44.1 65.6 7-1 6. Boise St MWC 7 22.7 41.2 63.9 7-0 7. Oregon P12 8 20.7 42.0 62.7 7-1 8. Wisconsin B10 8 21.5 38.0 59.5 6-2 9. Michigan B10 8 17.4 40.6 57.9 7-1 10. Texas A&M B12 8 9.9 46.3 56.2 5-3 11. Arizona St P12 8 13.1 42.7 55.8 6-2 12. Notre Dame IND 8 9.1 45.6 54.8 5-3 13. Nebraska B10 8 12.3 42.4 54.8 7-1 14. Houston CUS 8 22.9 30.5 53.4 8-0 15. Missouri B12 8 5.8 47.6 53.3 4-4 16. South Carolina SEC 8 11.4 41.5 52.9 7-1 17. Michigan St B10 8 9.1 43.7 52.9 6-2 18. Texas B12 7 8.7 44.1 52.8 5-2 19. Clemson ACC 9 12.1 40.2 52.3 8-1 20. Georgia SEC 8 9.1 43.1 52.3 6-2 21. Southern Cal P12 8 5.5 46.7 52.2 6-2 22. TCU MWC 8 16.2 34.7 50.9 6-2 23. Ohio State B10 8 5.8 44.7 50.5 5-3 24. Arkansas SEC 8 12.3 37.8 50.0 7-1 25. Toledo MAC 8 9.8 40.1 49.8 5-3 26. Florida St ACC 8 14.1 35.5 49.6 5-3 27. Virginia Tech ACC 9 11.9 37.5 49.4 8-1 28. Penn State B10 9 8.4 40.8 49.3 8-1 29. Kansas St B12 8 6.4 42.6 49.0 7-1 30. Cincinnati BgE 7 17.4 31.5 48.9 6-1 31. Baylor B12 7 3.5 45.1 48.6 4-3 32. Southern Miss CUS 8 15.8 32.4 48.1 7-1 33. West Virginia BgE 8 9.9 38.0 48.0 6-2 34. Georgia Tech ACC 9 12.7 34.7 47.4 7-2 35. Florida SEC 8 3.9 43.4 47.3 4-4 36. Tennessee SEC 8 -2.4 49.3 47.0 3-5 37. Miami FL ACC 8 5.0 41.6 46.6 4-4 38. Temple MAC 8 14.9 31.3 46.2 5-3 39. Illinois B10 9 6.2 39.7 45.9 6-3 40. Washington P12 8 3.0 42.8 45.8 6-2 41. North Carolina ACC 9 5.3 39.8 45.1 6-3 42. Tulsa CUS 8 4.0 40.9 44.9 5-3 43. Auburn SEC 9 -0.3 45.3 44.9 6-3 44. Mississippi St SEC 8 4.8 40.0 44.7 4-4 45. South Florida BgE 7 8.0 36.5 44.5 4-3 46. Utah P12 8 1.1 42.9 43.9 4-4 47. Texas Tech B12 8 4.9 38.9 43.9 5-3 48. Arizona P12 8 -5.1 48.6 43.6 2-6 49. Vanderbilt SEC 8 1.1 42.3 43.4 4-4 50. Iowa B10 8 9.2 34.0 43.2 5-3 51. San Diego St MWC 7 3.2 39.6 42.8 4-3 52. Rutgers BgE 8 7.3 35.5 42.8 5-3 53. Nevada WAC 8 4.9 37.3 42.2 5-3 54. SMU CUS 8 3.0 38.7 41.7 5-3 55. Pittsburgh BgE 8 1.1 40.1 41.2 4-4 56. California P12 8 0.8 40.1 41.0 4-4 57. Arkansas St Sun 8 9.6 31.0 40.5 6-2 58. Air Force MWC 8 2.3 38.0 40.3 4-4 59. Brigham Young IND 9 3.2 37.1 40.3 6-3 60. Iowa St B12 8 -6.8 46.4 39.6 4-4 61. Purdue B10 8 2.3 37.2 39.4 4-4 62. Northern Illinois MAC 8 6.4 32.5 38.9 5-3 63. Utah St WAC 7 4.4 34.4 38.8 2-5 64. UCLA P12 8 -6.8 45.4 38.6 4-4 65. Louisiana Tech WAC 8 0.6 38.0 38.6 4-4 66. Syracuse BgE 8 0.6 37.9 38.5 5-3 67. Northwestern B10 8 0.5 37.4 37.9 3-5 68. Virginia ACC 8 1.5 36.3 37.8 5-3 69. Washington St P12 8 -0.4 38.1 37.7 3-5 70. Louisville BgE 8 0.3 37.3 37.5 4-4 71. Ohio U. MAC 8 10.9 26.6 37.5 5-3 72. Western Michigan MAC 9 4.1 33.4 37.5 5-4 73. Wake Forest ACC 8 1.4 36.0 37.4 5-3 74. Hawai`i WAC 8 7.2 29.9 37.0 5-3 75. Navy IND 8 -3.3 40.0 36.7 2-6 76. Central Florida CUS 8 8.9 26.5 35.4 4-4 77. North Carolina St ACC 8 -0.9 36.3 35.4 4-4 78. Oregon St P12 8 -7.1 42.5 35.4 2-6 79. Maryland ACC 8 -8.3 43.4 35.2 2-6 80. Mississippi SEC 8 -9.4 44.5 35.1 2-6 81. Fresno St WAC 8 -5.1 40.1 35.0 3-5 82. Connecticut BgE 8 -0.3 35.1 34.8 3-5 83. UTEP CUS 8 -0.6 34.8 34.3 4-4 84. Wyoming MWC 7 1.1 33.0 34.1 5-2 85. Marshall CUS 9 -5.7 39.5 33.9 4-5 86. Florida Int'l Sun 8 2.8 31.1 33.9 5-3 87. Louisiana-Lafayette Sun 9 5.2 28.3 33.6 7-2 88. Bowling Green MAC 9 -1.1 34.3 33.2 4-5 89. San José St WAC 8 -6.4 39.4 33.0 3-5 90. Miami OH MAC 8 -4.6 37.3 32.8 3-5 91. Boston College ACC 8 -5.7 38.0 32.3 2-6 92. Duke ACC 8 -5.4 37.7 32.2 3-5 93. East Carolina CUS 8 -3.9 35.6 31.7 4-4 94. Kentucky SEC 8 -9.4 40.7 31.3 3-5 95. Ball St MAC 9 -6.7 37.7 31.0 5-4 96. Colorado P12 9 -16.6 46.8 30.2 1-8 97. Army IND 8 -0.4 30.4 30.0 3-5 98. Minnesota B10 8 -13.8 43.6 29.8 2-6 99. Eastern Michigan MAC 8 -2.6 32.1 29.4 5-3 100.Rice CUS 8 -13.0 41.9 28.9 2-6 101.Kansas B12 8 -19.4 47.8 28.4 2-6 102.Western Kentucky Sun 8 -2.4 30.4 28.0 4-4 103.New Mexico St WAC 8 -3.8 31.6 27.8 3-5 104.Louisiana-Monroe Sun 8 -5.9 33.2 27.3 2-6 105.Kent St MAC 8 -12.1 39.0 26.9 2-6 106.North Texas Sun 9 -11.7 38.4 26.8 3-6 107.Indiana B10 9 -12.4 38.9 26.6 1-8 108.Buffalo MAC 9 -10.4 36.9 26.5 2-7 109.Idaho WAC 8 -9.4 35.6 26.1 1-7 110.Middle Tennessee St Sun 7 -4.0 29.3 25.3 2-5 111.Central Michigan MAC 9 -7.6 32.6 25.1 3-6 112.Troy Sun 7 -9.5 34.3 24.8 2-5 113.Colorado St MWC 8 -5.4 29.5 24.1 3-5 114.UNLV MWC 7 -18.0 37.7 19.7 2-5 115.Akron MAC 8 -15.5 33.5 18.0 1-7 116.Florida Atlantic Sun 7 -19.2 37.0 17.7 0-7 117.Alabama-Birmingham CUS 8 -17.3 34.8 17.6 1-7 118.Tulane CUS 9 -11.9 27.8 15.9 2-7 119.Memphis CUS 9 -16.0 29.9 13.9 2-7 120.New Mexico MWC 8 -26.9 39.4 12.5 0-8

Here are the same standings but listed by conference:

Rk Team Con G MOV SOS SRS W-L 19. Clemson ACC 9 12.1 40.2 52.3 8-1 26. Florida St ACC 8 14.1 35.5 49.6 5-3 27. Virginia Tech ACC 9 11.9 37.5 49.4 8-1 34. Georgia Tech ACC 9 12.7 34.7 47.4 7-2 37. Miami FL ACC 8 5.0 41.6 46.6 4-4 41. North Carolina ACC 9 5.3 39.8 45.1 6-3 68. Virginia ACC 8 1.5 36.3 37.8 5-3 73. Wake Forest ACC 8 1.4 36.0 37.4 5-3 77. North Carolina St ACC 8 -0.9 36.3 35.4 4-4 79. Maryland ACC 8 -8.3 43.4 35.2 2-6 91. Boston College ACC 8 -5.7 38.0 32.3 2-6 92. Duke ACC 8 -5.4 37.7 32.2 3-5 8. Wisconsin B10 8 21.5 38.0 59.5 6-2 9. Michigan B10 8 17.4 40.6 57.9 7-1 13. Nebraska B10 8 12.3 42.4 54.8 7-1 17. Michigan St B10 8 9.1 43.7 52.9 6-2 23. Ohio State B10 8 5.8 44.7 50.5 5-3 28. Penn State B10 9 8.4 40.8 49.3 8-1 39. Illinois B10 9 6.2 39.7 45.9 6-3 50. Iowa B10 8 9.2 34.0 43.2 5-3 61. Purdue B10 8 2.3 37.2 39.4 4-4 67. Northwestern B10 8 0.5 37.4 37.9 3-5 98. Minnesota B10 8 -13.8 43.6 29.8 2-6 107.Indiana B10 9 -12.4 38.9 26.6 1-8 3. Oklahoma St B12 8 22.0 45.2 67.2 8-0 5. Oklahoma B12 8 21.5 44.1 65.6 7-1 10. Texas A&M B12 8 9.9 46.3 56.2 5-3 15. Missouri B12 8 5.8 47.6 53.3 4-4 18. Texas B12 7 8.7 44.1 52.8 5-2 29. Kansas St B12 8 6.4 42.6 49.0 7-1 31. Baylor B12 7 3.5 45.1 48.6 4-3 47. Texas Tech B12 8 4.9 38.9 43.9 5-3 60. Iowa St B12 8 -6.8 46.4 39.6 4-4 101.Kansas B12 8 -19.4 47.8 28.4 2-6 30. Cincinnati BgE 7 17.4 31.5 48.9 6-1 33. West Virginia BgE 8 9.9 38.0 48.0 6-2 45. South Florida BgE 7 8.0 36.5 44.5 4-3 52. Rutgers BgE 8 7.3 35.5 42.8 5-3 55. Pittsburgh BgE 8 1.1 40.1 41.2 4-4 66. Syracuse BgE 8 0.6 37.9 38.5 5-3 70. Louisville BgE 8 0.3 37.3 37.5 4-4 82. Connecticut BgE 8 -0.3 35.1 34.8 3-5 Rk Team Con G MOV SOS SRS W-L 14. Houston CUS 8 22.9 30.5 53.4 8-0 32. Southern Miss CUS 8 15.8 32.4 48.1 7-1 42. Tulsa CUS 8 4.0 40.9 44.9 5-3 54. SMU CUS 8 3.0 38.7 41.7 5-3 76. Central Florida CUS 8 8.9 26.5 35.4 4-4 83. UTEP CUS 8 -0.6 34.8 34.3 4-4 85. Marshall CUS 9 -5.7 39.5 33.9 4-5 93. East Carolina CUS 8 -3.9 35.6 31.7 4-4 100.Rice CUS 8 -13.0 41.9 28.9 2-6 117.Alabama-Birmingham CUS 8 -17.3 34.8 17.6 1-7 118.Tulane CUS 9 -11.9 27.8 15.9 2-7 119.Memphis CUS 9 -16.0 29.9 13.9 2-7 12. Notre Dame IND 8 9.1 45.6 54.8 5-3 59. Brigham Young IND 9 3.2 37.1 40.3 6-3 75. Navy IND 8 -3.3 40.0 36.7 2-6 97. Army IND 8 -0.4 30.4 30.0 3-5 25. Toledo MAC 8 9.8 40.1 49.8 5-3 38. Temple MAC 8 14.9 31.3 46.2 5-3 62. Northern Illinois MAC 8 6.4 32.5 38.9 5-3 71. Ohio U. MAC 8 10.9 26.6 37.5 5-3 72. Western Michigan MAC 9 4.1 33.4 37.5 5-4 88. Bowling Green MAC 9 -1.1 34.3 33.2 4-5 90. Miami OH MAC 8 -4.6 37.3 32.8 3-5 95. Ball St MAC 9 -6.7 37.7 31.0 5-4 99. Eastern Michigan MAC 8 -2.6 32.1 29.4 5-3 105.Kent St MAC 8 -12.1 39.0 26.9 2-6 108.Buffalo MAC 9 -10.4 36.9 26.5 2-7 111.Central Michigan MAC 9 -7.6 32.6 25.1 3-6 115.Akron MAC 8 -15.5 33.5 18.0 1-7 6. Boise St MWC 7 22.7 41.2 63.9 7-0 22. TCU MWC 8 16.2 34.7 50.9 6-2 51. San Diego St MWC 7 3.2 39.6 42.8 4-3 58. Air Force MWC 8 2.3 38.0 40.3 4-4 84. Wyoming MWC 7 1.1 33.0 34.1 5-2 113.Colorado St MWC 8 -5.4 29.5 24.1 3-5 114.UNLV MWC 7 -18.0 37.7 19.7 2-5 120.New Mexico MWC 8 -26.9 39.4 12.5 0-8 4. Stanford P12 8 27.4 39.2 66.5 8-0 7. Oregon P12 8 20.7 42.0 62.7 7-1 11. Arizona St P12 8 13.1 42.7 55.8 6-2 21. Southern Cal P12 8 5.5 46.7 52.2 6-2 40. Washington P12 8 3.0 42.8 45.8 6-2 46. Utah P12 8 1.1 42.9 43.9 4-4 48. Arizona P12 8 -5.1 48.6 43.6 2-6 56. California P12 8 0.8 40.1 41.0 4-4 64. UCLA P12 8 -6.8 45.4 38.6 4-4 69. Washington St P12 8 -0.4 38.1 37.7 3-5 78. Oregon St P12 8 -7.1 42.5 35.4 2-6 96. Colorado P12 9 -16.6 46.8 30.2 1-8 1. LSU SEC 8 24.5 43.9 68.4 8-0 2. Alabama SEC 8 27.4 40.7 68.1 8-0 16. South Carolina SEC 8 11.4 41.5 52.9 7-1 20. Georgia SEC 8 9.1 43.1 52.3 6-2 24. Arkansas SEC 8 12.3 37.8 50.0 7-1 35. Florida SEC 8 3.9 43.4 47.3 4-4 36. Tennessee SEC 8 -2.4 49.3 47.0 3-5 43. Auburn SEC 9 -0.3 45.3 44.9 6-3 44. Mississippi St SEC 8 4.8 40.0 44.7 4-4 49. Vanderbilt SEC 8 1.1 42.3 43.4 4-4 80. Mississippi SEC 8 -9.4 44.5 35.1 2-6 94. Kentucky SEC 8 -9.4 40.7 31.3 3-5 57. Arkansas St Sun 8 9.6 31.0 40.5 6-2 86. Florida Int'l Sun 8 2.8 31.1 33.9 5-3 87. Louisiana-Lafayette Sun 9 5.2 28.3 33.6 7-2 102.Western Kentucky Sun 8 -2.4 30.4 28.0 4-4 104.Louisiana-Monroe Sun 8 -5.9 33.2 27.3 2-6 106.North Texas Sun 9 -11.7 38.4 26.8 3-6 110.Middle Tennessee St Sun 7 -4.0 29.3 25.3 2-5 112.Troy Sun 7 -9.5 34.3 24.8 2-5 116.Florida Atlantic Sun 7 -19.2 37.0 17.7 0-7 53. Nevada WAC 8 4.9 37.3 42.2 5-3 63. Utah St WAC 7 4.4 34.4 38.8 2-5 65. Louisiana Tech WAC 8 0.6 38.0 38.6 4-4 74. Hawai`i WAC 8 7.2 29.9 37.0 5-3 81. Fresno St WAC 8 -5.1 40.1 35.0 3-5 89. San José St WAC 8 -6.4 39.4 33.0 3-5 103.New Mexico St WAC 8 -3.8 31.6 27.8 3-5 109.Idaho WAC 8 -9.4 35.6 26.1 1-7

Again, these rankings are far from perfect. But at least in theory, they’re pretty simple and easy to understand. They don’t get at everything we want to know, but you can quickly scan any team’s line and get a good sense of how their season has been. Each team’s rating is simply the sum of their (adjusted) margin of victory and their sum of their opponent’s average (adjusted) MOV. The SRS puts equal weight on all games, something the brain is not wont to do.

By way of example, let’s look at the craziness Texas Tech fans have had to deal with the past three weeks. Against Kansas State (SRS rating of 49.0), the Red Raiders lost at home by 7, so that grade counts as a 39 for purposes of the SRS. Then playing in Norman against the Sooners (SRS of 65.6), Tech somehow managed to upend Oklahoma by three points (+7 adjusted MOV, for an SRS grade of 72.6). This past weekend, the second worst team in the conference, Iowa State (SRS of 39.6), blew the doors off of Texas Tech, 41-7. That goes down as an adjusted MOV of -30.5, for an SRS grade of 9.1. There’s no way to make sense of a team with SRS grades of 39.0, 72.6 and 9.1 in three consecutive weeks.

One thing the SRS and almost everyone else agrees on: it’s pretty hard to separate LSU from Alabama.