SRS Details

Each week, the Scissom Ranking System results are posted with a variety of data points. Most of the headers are abbreviated, below I detail the meaning of each data point as well as how each data point is derived. I include formulas for some of the basic functions, but omit the main ranking formula.

The data points are:

• Points
• Strength of Schedule
• pStrength
• rStrength
• OOC pStrength
• OOC rStrength
• Ranking
• SP
• PPS
• SUM

 

Points

The Scissom Ranking System was designed as a college football ranking system that considers margin of victory in such a way that 'blowing out' inferior opponents does not disproportionally benefit a team, but allows for significant wins against tough opponents to mean more than just a win. For example, in the BCS, margin of victory was not allowed as a data point. Therefore, the #1 team beating the #2 teams by 3 points carries the same weight as the #1 team beating an unranked team by the same margin. The same would go for the #1 team beating the #2 team by 40 points while beating an unranked team by the same margin. Both wins are equal.

By using a ratio (loser/winner) to compare the two teams playing, the SRS can use the margin of victory in such a way that it is significant and doesn't benefit a team for beating up on inferior opponents.

For Example: 

Favored Team wins:

Using Week 14 results from the SRS
#1 Alabama (344.03) vs #2 Oregon (341.58)
 If Alabama wins by 7, the ratio is: Oregon / Alabama or 341.58 / 344.03 = .993

This ratio is then used to calculate the new points for both teams using the following formula:
Alabama Points = Initial Points + ratio * 10 + ratio * margin
Alabama Points = 344.03 + .993 * 10 + .993 * 7 = 360.911

Oregon Points = Initial Points - ratio * 10 - ratio * margin
Oregon Points = 341.58 - .993 * 10 - .993 * 7 = 324.699

 To Compare:

Using Week 14 results from the SRS
#1 Alabama (344.03) vs #156 Vanderbilt (38.53)
If Alabama wins by the same margin as above (7), the ratio is: Vanderbilt / Alabama or 38.53 / 344.03 =  .11

This ratio is then used to calculate the new points for both teams using the same formula: 
Alabama Points = 344.03 + .11* 10 + .11* 7 = 345.9

Vanderbilt Points = 38.53 - .11 * 10 - .11 * 7 = 36.66

 Visually

Underdog Team wins:

Using Week 14 results from the SRS
#1 Alabama (344.03) vs #2 Oregon (341.58)
 If Alabama loses by 7, the ratio is: Alabama / Oregon or 344.03 / 341.58 = 1.01

This ratio is then used to calculate the new points for both teams using the following formula:
Alabama Points = Initial Points - ratio * 10 - ratio * margin
Alabama Points = 344.03 - 1.01 * 10 - 1.01 * 7 = 326.86

Oregon Points = Initial Points + ratio * 10 + ratio * margin
Oregon Points = 341.58 + 1.01 * 10 + 1.01 * 7 =358.75

 To Compare:

Using Week 14 results from the SRS
#1 Alabama (344.03) vs #156 Vanderbilt (38.53)
If Alabama loses by the same margin as above (7), the ratio is: Alabama / Vanderbilt or 344.03 / 38.53 = 8.93

This ratio is then used to calculate the new points for both teams using the same formula: 
Alabama Points = 344.03 - 8.93 * 10 - 8.93 * 7 = 192.22* (277.03)

Vanderbilt Points = 38.53 + 8.93 * 10 + 8.93 * 7 = 190.34* (102.53)

* - The most any team can increase or decrease each week is +/- 60 + margin of victory, so these values would be modified to represent that limit (in parenthesis above)

Visually

Strength of Schedule

Strength of Schedule is calculated the same way for 4 different values:

• pStrength: The average point value of all opponents played to this point in the season.
• rStrength: The average ranking value of all opponents played to this point in the season (discussed later)
• OOC pStrength and OOC rStrength: Same as above, but only referencing Out of Conference opponents.

Ranking

The ranking value is the actual value that is used to evaluate each team. The ranking value takes in the following data points:

•  Points
• Win/Loss Record
• Win Percentage
• pStrength 

While the ranking formula is secret, it can roughly be estimated as  60% Points, 35% Strength of Schedule, and 5% other factors.

SP and PPS

SP is Scoring Potential. It is calculated using the following formula:

Total Points Scored / (1000 - SOS)

PPS is the Potential to Prevent Scoring. It is calculated using the following formula:

1 - (Total Points Allowed / (1000 - SOS))

The reason this isn't named offensive and defense ratings (as it was initially) is because this is only the rating of the offense and defense against the teams they've played. That is significant, because regularly, division II teams have very high SP and PPS ratings. As of Week 14 of 2014, Harvard has the highest PPS at .87. For reference, Clemson has given up the fewest yards at this point in the season and their PPS is .74.

SUM

Sum is just a reference value, much like slugging percentage in baseball, that is the sum of SP and PPS.