Nebraska and Offensive Efficiency – Part I

Earlier I introduced to the Bendability Index, a measure of defensive efficiency and one of the “Stats That Matter” at Cold, Hard Football Facts. Today I want to switch sides of the ball and look at offensive efficiency. Cold, Hard Football Facts has a stat for that as well. This is measure is known as the Scorability Index.

According to the site:

Scoreability Index – This is the offensive counterpart of the Bendability Index. The Scoreability Index is obtained by dividing a team’s total yards by total points scored, yielding Yards Per Point Scored. A team that ranks high on the Scoreability Index has the offense that scores most efficiently, marching off a relatively small number of yards for every point it scores. This effort is more important than total offense and, in many cases, more important than scoring offense. The Scoreability Index is not purely an offensive yardstick. It is, instead, a great barometer of team success. It is a function of many team-wide factors, including general offensive strength, defense and special teams proficiency, turnover differential and Red Zone offense.

To help explain how this variable works in the NFL, Cold, Hard Football Facts uses the incompetence of the Raiders offense:

Pity poor Oakland. The Raiders will not only go down as one of the most inept offenses in modern NFL history, scoring just 10.5 PPG and averaging a dreadful 4.4 yards everytime they dropped back to pass, they also wasted a lot of effort this season moving the ball up and down the field for no reason.

Oakland needed to generate 23.45 yards to score a single point this season. That’s more than twice the effort expended by division rival San Diego, which needed just 11.87 yards to score a single point.

To put it in more concrete football terms, the Chargers scored one touchdown for every 71 yards of offense they generated. The Raiders scored one touchdown for every 140 yards of offense they generated.

As a result, one team has the best record in football. The other team has the worst record in football.

That’s a pretty telling statistic in the NFL, but what about in college football? To find out, I again constructed a spreadsheet ranking NCAA teams in terms of the Scoreability Index for 2006. Next I used SMQ’s methodology for determining the relevance of a particular statistic in CFB. This meant finding the winning percentage of the Top 20 teams in the Scoreability Index category, as well as the winning percentage of the Bottom 20 teams in the Scoreability Index.

According to SMQ this is important because:

“…the relevance of a statistic shouldn’t be measured only by the relative success of teams that perform well in a given category, but also by the relative failure of those that don’t.”

Next, I calculated what SMQ sees as the most relevant measure of this analysis, the relationship between the winning percentages on the high and low ends of the Scoreability Index. In other words, I subtracted the winning percentage of teams in the Bottom 20 of the Scoreability Index from the winning percentage of the teams in the Top 20 of the Scoreability Index to determine the relative disparity between these two groups. From a statistical standpoint, the greater the level of disparity, the more relevant the particular statistic. Or as a SMQ noted:

“the ‘most important’ category, it would follow, would be the one with the best records at the top, the worst records at the bottom and, therefore, the greatest disparity.”

SMQ’s analysis (along with my own additional calculations) found the most relevant offensive statistics based on disparity to be:

Third Down Efficiency +.477
Total Offense +.473
Scoring Offense +.472
Yards/Pass Attempt +.389
Passing Efficiency +.377
Rush Offense +.360
Fourth Down Efficiency +.350
Pass Offense +.182
Time of Possession +.164

Calculating the disparity margin of the Scoreability Index produced a figure of +.485. This means that the Scoreability Index produces the most relevant offensive statistic in terms of winning percentage.

So, just to clarify again:

The Scoreability Index is obtained by dividing a team’s total yards by total points scored, yielding Yards Per Point Scored. A team that ranks high on the Scoreability Index has the offense that scores most efficiently, marching off a relatively small number of yards for every point it scores.

This is another interesting statistic and I believe it makes sense to think about teams in terms of how hard they are working to put points up on the board. We also have some evidence that this statistic is relevant in CFB. In fact, it looks to be more important than some of the statistics folks around Nebraska continue to harp on way too much – most notably, Time of Possession and Rushing Offense. These two statistics just didn’t matter in college football in 2006. But the Scoreability Index did. In Part II of this series I will look at how the teams ranked nationally in terms of the Scoreability Index. I will also examine where Nebraska fits in with regard to this statistic.

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