KRACH 19 Nov 2009 - Addresses most of the problems from last week

Submitted by quakk on November 18th, 2009 at 4:06 PM
EDIT:  Added further justification to point 5.

I put a bit of effort in cleaning up my code to address some of the problems from last week:
  1. Undefeated and winless teams:  I added the fictitious tie.  Now there's a path from every team to every other team.  While this is a hack, it's reasonable and about as far as I really care to go with it.  I also calculated the round-robin winning percentage (RRWP) and KRACH strength of schedule (SOS).  These are useful metrics for comparing teams that don't line up very well, as per John Whelan's KRACH site.  Now the undefeated and winless teams can be compared with multiple data elements.
  2. Rasmus:  Open source:  The original Pairwise and KRACH code was freely given to me years ago by John Whelan.  This code is my own, based only on the information given in his KRACH site;  given that, I'm comfortable sharing my code, so long as the user gives due credit to John and Ken Butler.
  3. joeyb:  Undefeated teams will always rate better than teams with losses:  To investigate this, I created a fictitious team that was 10-0 with wins against only the bottom ten teams.  It rated out at #37, well below several 1- and 2-loss teams.
  4. SpartanDan:  Top teams are ranked backwards:  You are correct, sir.  I mistakenly assumed that a larger deviation from predicted meant a less accurate KRACH.  This has been fixed, as in 1) above, with the RRWP, SOS and fictitious tie.
  5. Seth9:  The rating doesn't apply to college football:  You may be right on this. It's still curious, and now trivial, for me to crunch the numbers.  EDIT:  But is this any less applicable than any of the computer ratings used in the BCS?  And it certainly does not have the bias and politicking associated with opinion polls.
As points of comparison, I've included the latest BlogPoll results and BCS standings.

Again, this rating includes all D-IA games through 15 November 2009:

Team BlogPoll BCS Rank KRACH RRWP Record Rank W L T Win % SOS Rank SOS
Alabama 1 2 1 50.413 0.953 1 10 0 0 1.000 10 2.401
Florida 3 1 2 43.477 0.946 1 9 0 0 1.000 15 2.288
Cincinnati 5 5 3 36.050 0.937 1 9 0 0 1.000 23 1.897
TCU 4 4 4 29.380 0.926 1 9 0 0 1.000 35 1.546
Texas 2 3 5 26.406 0.920 1 10 0 0 1.000 52 1.257
Boise State 6 6 6 21.243 0.906 1 9 0 0 1.000 59 1.118
Georgia Tech 7 7 7 13.464 0.870 2 9 1 0 0.900 18 2.126
LSU 11 8 8 9.599 0.837 5 8 2 0 0.800 2 2.823
Oregon 9 11 9 9.141 0.832 5 8 2 0 0.800 3 2.688
Pittsburgh 8 9 10 8.655 0.826 3 8 1 0 0.889 37 1.527
Ohio State 10 10 11 7.289 0.807 4 9 2 0 0.818 22 1.918
Iowa 14 13 12 6.292 0.789 5 8 2 0 0.800 24 1.851
Virginia Tech 16 15 13 6.103 0.785 8 7 3 0 0.700 1 2.848
Oklahoma State 12 12 14 5.436 0.770 6 7 2 0 0.778 26 1.812
Penn State 15 14 15 5.061 0.761 5 8 2 0 0.800 40 1.489
Oregon State 19 19 16 4.967 0.758 9 6 3 0 0.667 4 2.675
USC 21 18 17 4.954 0.758 8 7 3 0 0.700 14 2.312
Wisconsin 17 16 18 4.574 0.747 6 7 2 0 0.778 38 1.525
Miami (FL) 20 20 19 4.544 0.746 9 6 3 0 0.667 8 2.447
Clemson 18 23 20 4.393 0.741 9 6 3 0 0.667 12 2.365
Rutgers

21 4.372 0.741 7 5 2 0 0.714 20 1.987
Utah 23 21 22 3.965 0.727 5 8 2 0 0.800 56 1.166
Stanford 13 17 23 3.825 0.721 8 7 3 0 0.700 27 1.785
California
25 24 3.679 0.716 9 6 3 0 0.667 21 1.981
Temple

25 3.607 0.713 3 8 1 0 0.889 88 0.636
North Carolina 25
26 3.504 0.708 11 5 3 0 0.625 16 2.230
Arizona

27 3.496 0.708 11 5 3 0 0.625 17 2.224
Georgia

28 3.049 0.687 14 5 4 0 0.556 7 2.494
South Florida

29 3.048 0.687 13 4 3 0 0.571 11 2.370
Navy

30 3.001 0.685 8 7 3 0 0.700 46 1.400
Brigham Young 22 22 31 2.900 0.680 5 8 2 0 0.800 71 0.853
Boston College

32 2.855 0.677 9 6 3 0 0.667 36 1.537
Arkansas

33 2.826 0.675 14 5 4 0 0.556 13 2.312
Houston 24 24 34 2.817 0.675 6 7 2 0 0.778 63 0.939
West Virginia

35 2.665 0.666 9 6 3 0 0.667 41 1.435
Auburn

36 2.379 0.648 12 6 4 0 0.600 31 1.647
Notre Dame

37 2.252 0.639 12 6 4 0 0.600 33 1.559
Mississippi

38 2.228 0.637 11 5 3 0 0.625 43 1.418
Central Michigan

39 2.091 0.627 6 7 2 0 0.778 84 0.697
Nebraska

40 1.994 0.619 8 7 3 0 0.700 64 0.931
Florida State

41 1.985 0.618 16 4 5 0 0.444 9 2.426
South Carolina

42 1.748 0.597 15 5 5 0 0.500 28 1.748
Kentucky

43 1.717 0.594 14 5 4 0 0.556 44 1.405
Oklahoma

44 1.709 0.593 14 5 4 0 0.556 47 1.398
UCLA

45 1.680 0.590 15 5 5 0 0.500 29 1.680
Tennessee

46 1.648 0.587 15 5 5 0 0.500 30 1.648
Minnesota

47 1.549 0.576 15 5 5 0 0.500 34 1.549
Missouri

48 1.498 0.570 14 5 4 0 0.556 54 1.225
Troy

49 1.447 0.564 8 7 3 0 0.700 86 0.675
Texas Tech

50 1.400 0.559 14 5 4 0 0.556 57 1.145
Mississippi State

51 1.372 0.555 20 3 6 0 0.333 5 2.548
Connecticut

52 1.289 0.544 18 3 5 0 0.375 19 2.026
Air Force

53 1.239 0.537 12 6 4 0 0.600 70 0.858
Michigan State

54 1.223 0.535 15 5 5 0 0.500 55 1.223
Washington

55 1.187 0.530 21 3 7 0 0.300 6 2.543
Nevada

56 1.179 0.529 8 7 3 0 0.700 95 0.550
Fresno State

57 1.152 0.525 14 5 4 0 0.556 62 0.942
Northwestern

58 1.151 0.525 12 6 4 0 0.600 76 0.797
UCF

59 1.125 0.521 14 5 4 0 0.556 65 0.921
East Carolina

60 1.061 0.510 14 5 4 0 0.556 69 0.868
Duke

61 1.056 0.509 15 4 4 0 0.500 60 1.056
Arizona State

62 0.993 0.499 20 3 6 0 0.333 25 1.845
Idaho

63 0.961 0.493 10 7 4 0 0.636 92 0.577
Middle Tennessee State

64 0.943 0.490 8 7 3 0 0.700 102 0.440
Southern Methodist

65 0.924 0.486 14 5 4 0 0.556 80 0.756
Iowa State

66 0.874 0.477 15 5 5 0 0.500 67 0.874
Virginia

67 0.820 0.466 20 3 6 0 0.333 39 1.523
Southern Miss

68 0.787 0.459 14 5 4 0 0.556 87 0.644
Texas A&M

69 0.757 0.452 15 5 5 0 0.500 79 0.757
Wake Forest

70 0.757 0.452 21 3 7 0 0.300 32 1.622
Baylor

71 0.738 0.447 20 3 6 0 0.333 48 1.370
Purdue

72 0.736 0.447 19 4 7 0 0.364 53 1.227
Louisville

73 0.726 0.445 20 3 6 0 0.333 49 1.348
Kansas State

74 0.718 0.443 16 4 5 0 0.444 66 0.878
Kansas

75 0.683 0.434 16 4 5 0 0.444 73 0.835
Northern Illinois

76 0.675 0.432 9 6 3 0 0.667 108 0.364
Bowling Green

77 0.624 0.419 15 5 5 0 0.500 89 0.624
Ohio

78 0.624 0.419 9 6 3 0 0.667 113 0.336
Marshall

79 0.612 0.415 16 4 5 0 0.444 81 0.748
Louisiana-Monroe

80 0.578 0.406 14 5 4 0 0.556 99 0.473
Michigan

81 0.577 0.406 17 4 6 0 0.400 74 0.833
Wyoming

82 0.564 0.402 16 4 5 0 0.444 85 0.689
UAB

83 0.511 0.385 15 5 5 0 0.500 97 0.511
North Carolina State

84 0.510 0.385 22 2 6 0 0.250 50 1.326
Syracuse

85 0.476 0.374 23 2 7 0 0.222 42 1.428
Indiana

86 0.407 0.349 21 3 7 0 0.300 68 0.872
Colorado

87 0.390 0.342 21 3 7 0 0.300 72 0.835
Illinois

88 0.380 0.338 23 2 7 0 0.222 58 1.140
UNLV

89 0.363 0.331 21 3 7 0 0.300 78 0.777
Toledo

90 0.324 0.313 17 4 6 0 0.400 100 0.468
Colorado State

91 0.314 0.309 23 2 7 0 0.222 61 0.943
San Diego State

92 0.303 0.303 20 3 6 0 0.333 93 0.562
Kent State

93 0.298 0.301 16 4 5 0 0.444 107 0.364
Louisiana-Lafayette

94 0.273 0.289 16 4 5 0 0.444 114 0.334
Western Michigan

95 0.243 0.272 17 4 6 0 0.400 111 0.351
Florida Atlantic

96 0.242 0.271 20 3 6 0 0.333 101 0.449
Maryland

97 0.226 0.262 26 1 8 0 0.111 51 1.282
Hawaii

98 0.223 0.260 20 3 6 0 0.333 103 0.413
Washington State

99 0.222 0.259 27 1 9 0 0.100 45 1.403
Tulsa

100 0.205 0.248 20 3 6 0 0.333 106 0.380
Louisiana Tech

101 0.204 0.248 23 2 7 0 0.222 90 0.611
Buffalo

102 0.185 0.235 23 2 7 0 0.222 94 0.555
UTEP

103 0.165 0.220 21 3 7 0 0.300 110 0.353
Army

104 0.162 0.218 20 3 6 0 0.333 116 0.300
Florida International

105 0.155 0.213 21 3 7 0 0.300 115 0.332
Tulane

106 0.136 0.197 23 2 7 0 0.222 104 0.407
Memphis

107 0.126 0.189 26 1 8 0 0.111 83 0.713
Vanderbilt

108 0.124 0.187 27 1 9 0 0.100 77 0.787
Utah State

109 0.117 0.180 23 2 7 0 0.222 112 0.350
Akron

110 0.107 0.171 26 1 8 0 0.111 91 0.606
Arkansas State

111 0.106 0.170 25 1 7 0 0.125 96 0.528
Miami (OH)

112 0.105 0.169 28 1 10 0 0.091 82 0.734
New Mexico State

113 0.079 0.141 23 2 7 0 0.222 118 0.236
Rice

114 0.076 0.138 27 1 9 0 0.100 98 0.479
North Texas

115 0.064 0.123 24 2 8 0 0.200 119 0.218
San Jose State

116 0.048 0.101 29 0 8 0 0.000 75 0.815
Ball State

117 0.032 0.074 26 1 8 0 0.111 120 0.179
New Mexico

118 0.019 0.049 29 0 10 0 0.000 105 0.395
Western Kentucky

119 0.019 0.049 29 0 9 0 0.000 109 0.353
Eastern Michigan

120 0.012 0.033 29 0 10 0 0.000 117 0.250

Comments

colin

November 18th, 2009 at 4:30 PM ^

a pretty ridiculous expected win percentage for OSU in The Game. I don't know if that's true for the rest of the games against the spread, but that would be worth finding out.

FWIW, OSU is something like 80% to win on Saturday based on the line. Ugh.

SpartanDan

November 18th, 2009 at 9:46 PM ^

KRACH doesn't know it's a rivalry game, for instance, nor does it know about Tressel's tendency to turtle as soon as he gets a two-score lead (all it sees is wins and losses, no matter how nail-biting or otherwise). Vegas does. Both of those increase the probabilities of a close game (the latter may not actually increase Michigan's chances of winning, though; just the chance of keeping it close), reducing the line. I'm also fairly certain it doesn't consider home field (again, Vegas certainly does).

Not knowing that this was a huge rivalry game and putting it at a neutral site, I'd probably agree with the 93% chance of an OSU win predicted by KRACH. With the rivalry and home field factored in, I'd bring that down a bit (probably not as far down as 80%, though - Tresselball is designed to minimize variance, which makes them far less vulnerable to upsets but also far less likely to pull one off themselves should they face a better team).

Out of curiosity, where do you get the line-to-%W conversion from? Or are you looking at the money line rather than the spread?