Stats That Matter: Pass Efficiency

Sometimes stats tell you things that everyone already knows.

Stats That Matter
* Part 1: Introduction
* Part 2: Bendability
* Part 3: Scoreability
* Part 4: Turnover Margin
* Part 5: Pass Efficiency
For example, it is not going to shock anyone to learn that No. 1 on our list of stats that correlate to winning is points per game differential. That's not really telling us anything, although it is good to get confirmation of the age-old joke that the team with the most points on the board at the end of the game wins.

However, sometimes stats sneak up on you and demonstrate a relevance that is undeniable, but only partially explainable. Such it is with passing efficiency differential. Remember, the stronger the correlation, the closer the coefficient approaches either the number "1" or "-1" – pass efficiency differential has a correlative value of 0.8284, the third-highest correlation of the stats we looked at.

What's more, when you look at the above list of the Top 20 teams of the past five years in pass efficiency differential you see arguably the Top 20 best teams of the past five years.

Of course these are just the BCS teams, I am sure Boise State and TCU would likely show up there as well if we had included non-BCS teams in our data. However, it's hard to think of many BCS teams over the past five years that are clearly better than the twenty on that list. Half of the teams on that list had one loss or less, all had double-digit wins and no team had more than three losses. These are teams that won BCS titles, played in BCS title games, won conference championships.

What happened to the cliché, "To win in college football, run the ball and stop the run"? Rushing yards-per-game checks in at 7th on our overall list, a tenth of point and four spots lower than pass efficiency differential.

What are we measuring here? We are measuring your completions, attempts, yards, touchdowns and interceptions and those of your opponents.

Of course, in a back door sort of way we're also including turnovers in this equation, since interceptions – yours and your opponents – are counted in the passing efficiency equation. But earlier this week we also discovered that, in the aggregate, turnover margin doesn't show up as a particularly influential factor – by itself it is only 14th overall among our 27 categories. So something besides factoring in interceptions is going on here.

As a further sign of the way Virginia Tech has dominated the ACC, the top four pass efficiency differential marks posted by the conference in the last five years against BCS teams all belong to Virginia Tech. The 2006 conference champ Wake Forest checks in with the fifth best mark over the past five years in the conference, and surprising Maryland made the list in 2010. The Tar Heels have two of the top ten conference marks in pass efficiency differential over BCS foes in the past five years, in 2008 and 2010.

The importance of this stat is a sign of the way college football has changed over the years. These days, you need to know how to throw the ball efficiently and defend efficiently.

That doesn't mean a team has to throw the ball often. From 2006-2010 Virginia Tech has finished 10th, 11th, 11th, 8th, and 11th in passing attempts in the ACC. In addition, Offensive Passing Yards Per Game has the weakest correlation to winning of all the stats we studied. What is does mean is that when you choose to throw the ball, do it efficiently.

The other half of the equation is to defend the pass efficiently, and that's yet another area where Virginia Tech has consistently excelled against BCS opponents. Over the last five years against BCS teams,Virginia Tech has posted three of the top ten best marks in the conference.

Had I not seen the data, I would not have guessed that UNC's best mark in the league in pass defense efficiency against BCS teams came in 2009, a third-place finish in the ACC in that category. I would have overestimated the effectiveness of the UNC secondary over the past three years, and that's clearly an area of the Tar Heels defense that needs to take a step forward.

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