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Data mining the divisional round

Posted by Doug on January 11, 2007

Last week I conconcted a rote algorithm for predicting playoff games based on comparing each matchup to historically similar playoff games. Now it's time to take a look at the divisional round.

The predictions are a bit surprising, with the algorithm projecting blowouts by the home team in three of the four games. I'll post the full lists of comparables below, but for now here are the predictions.


  • Chicago over Seattle by 17. Chicago has a 93% chance of winning.

  • San Diego over New England by 16. San Diego has an 87% chance of winning.

  • Baltimore over Indy by 12. Baltimore has a 72% chance of winning.

  • New Orleans over Philly by 3. New Orleans has a 60% chance.

Last week the algorithm was very close to the Vegas line on three of the four games. Not so this week. Personally, I generally agree with both NFC predictions, but I disagree with the algorithm on both AFC matchups. But a look at the history of divisional round matchups does explain why these predictions turned out like they did. Some simple queries about divisional round games since the 12-team format was introduced in 1990:


  • Home teams with a better record than their opponent are 49-9 in the divisional round. Home teams with a better record have outscored their opponents by an average of 12.4 points.

  • Home teams with a record one game better than their opponent (like Baltimore) are 16-5 with an average margin of 7.8 points.

  • Home teams with a record two games better than their opponent (like San Diego) are 12-1 with an average margin of 13.1 points.

  • Home teams with a record three or more games better than their opponent (like Chicago) are 21-3 with an average margin of 16 points.

Here are the full lists of comparables (to remind yourself what the column headers stand for, read last week's post):


TM YR R OPP W L6 SOS PD H B SIM Res
=======================================================
chi 4 1 -0.008 178 1 1
den 1998 d mia 4 1 -0.067 136 1 1 899 W 38- 3
sfo 1994 d chi 4 2 -0.017 245 1 1 824 W 44-15
den 2005 d nwe 3 1 0.004 96 1 1 805 W 27-13
kan 1995 d ind 4 0 0.033 102 1 1 782 L 7-10
dal 1994 d gnb 3 1 -0.033 71 1 1 767 W 35- 9
stl 1999 d min 3 1 -0.104 220 1 1 761 W 49-37
tam 2002 d sfo 2 1 -0.015 134 1 1 749 W 31- 6
pit 2001 d bal 3 1 -0.088 102 1 1 744 W 27-10
phi 2004 d min 5 2 -0.008 116 1 1 737 W 27-14
sfo 1997 d min 4 3 -0.033 115 1 1 711 W 38-22
stl 2001 c phi 3 1 0.000 95 1 0 709 W 29-24
dal 1993 d gnb 3 2 -0.013 89 1 1 706 W 27-17
phi 2002 d atl 3 2 -0.017 86 1 1 699 W 20- 6
oak 2002 d nyj 2 1 0.040 123 1 1 697 W 30-10
was 1991 d atl 4 -1 0.046 238 1 1 686 W 24- 7
WEIGHTED AVERAGE: 93.1 pct chance of victory
PROJECTED SCORE: 30.4-13.4

TM YR R OPP W L6 SOS PD H B SIM Res
=======================================================
sdg 2 1 -0.034 41 1 1
atl 1998 d sfo 2 1 -0.050 2 1 1 945 W 20-18
tam 2002 d sfo 2 1 -0.015 134 1 1 887 W 31- 6
sea 2005 c car 2 1 -0.012 49 1 0 870 W 34-14
dal 1994 d gnb 3 1 -0.033 71 1 1 869 W 35- 9
nyg 1990 d chi 2 1 0.083 56 1 1 867 W 31- 3
nwe 1996 d pit 1 1 -0.013 18 1 1 855 W 28- 3
min 1992 w was 2 1 -0.025 80 1 0 852 L 7-24
stl 2001 d gnb 2 1 0.050 106 1 1 851 W 45-17
oak 2002 d nyj 2 1 0.040 123 1 1 844 W 30-10
det 1991 d dal 1 1 -0.062 12 1 1 842 W 38- 6
phi 2001 w tam 2 1 -0.046 91 1 0 838 W 31- 9
chi 2001 d phi 2 0 -0.013 0 1 1 837 L 19-33
pit 1995 c ind 2 1 0.008 65 1 0 833 W 20-16
nwe 2004 d ind 2 0 0.000 6 1 1 831 W 20- 3
oak 2000 d mia 1 1 -0.071 83 1 1 821 W 27- 0
WEIGHTED AVERAGE: 86.8 pct chance of victory
PROJECTED SCORE: 27.7-11.4

TM YR R OPP W L6 SOS PD H B SIM Res
=======================================================
nor 0 -1 -0.016 21 1 1
oak 2001 w nyj 0 -1 -0.046 59 1 0 832 W 38-24
sfo 1997 c gnb 0 -1 0.008 -30 1 0 824 L 10-23
ind 1999 d ten 0 0 0.062 22 1 1 820 L 16-19
mia 1992 d sdg 0 -2 0.008 -35 1 1 819 W 31- 0
sfo 2002 w nyg 0 -1 0.023 -25 1 0 815 W 39-38
sfo 1993 d nyg -1 -1 -0.004 95 1 1 814 W 44- 3
gnb 1994 w det 0 -1 -0.046 80 1 0 811 W 16-12
ten 2000 d bal 1 -1 0.054 -13 1 1 795 L 10-24
mia 1998 w buf 0 -1 0.062 -11 1 0 789 W 24-17
sfo 1995 d gnb 0 0 0.013 109 1 1 783 L 17-27
chi 2005 d car 0 0 0.008 -74 1 1 780 L 21-29
oak 2000 c bal 0 -2 -0.004 12 1 0 779 L 3-16
sdg 1994 d mia 1 0 -0.029 13 1 1 778 W 22-21
ten 2002 d pit 1 0 -0.006 -2 1 1 767 W 34-31
buf 1992 w hou 1 -1 -0.037 4 1 0 761 W 41-38
WEIGHTED AVERAGE: 60.0 pct chance of victory
PROJECTED SCORE: 24.4-21.3

TM YR R OPP W L6 SOS PD H B SIM Res
=======================================================
bal 1 2 -0.037 85 1 1
hou 1993 d kan 1 2 -0.058 93 1 1 970 L 20-28
stl 2003 d car 1 2 -0.008 98 1 1 958 L 23-29
pit 1995 d buf 1 2 0.004 65 1 1 938 W 40-21
nyg 2000 c min 1 2 -0.042 56 1 0 866 W 41- 0
oak 2000 d mia 1 1 -0.071 83 1 1 864 W 27- 0
sdg 1992 w kan 1 2 -0.029 28 1 0 835 W 17- 0
nyj 1998 d jax 1 3 0.029 96 1 1 822 W 34-24
den 1991 d hou 1 2 -0.067 -66 1 1 819 W 26-24
nwe 1996 d pit 1 1 -0.013 18 1 1 808 W 28- 3
pit 1994 d cle 1 2 0.017 -54 1 1 807 W 29- 9
phi 2003 c car 1 2 0.037 66 1 0 806 L 3-14
car 1996 d dal 2 2 -0.104 113 1 1 804 W 26-17
pit 1994 c sdg 1 2 -0.017 7 1 0 801 L 13-17
det 1991 d dal 1 1 -0.062 12 1 1 801 W 38- 6
phi 2002 d atl 3 2 -0.017 86 1 1 778 W 20- 6
WEIGHTED AVERAGE: 72.1 pct chance of victory
PROJECTED SCORE: 25.8-13.5

This entry was posted on Thursday, January 11th, 2007 at 6:16 am and is filed under General. You can follow any responses to this entry through the RSS 2.0 feed. Both comments and pings are currently closed.