First, a warning: I am not a professional statistician or nearly as smart about this kind of stuff as this guy. So, I'm fulling willing to admit that I'm a hack playing around with mathematical concepts that, even if I don't fully understand how they work, I understand what their results signify (assuming I'm using them right).
I do have a pretty good head for numbers, though, and a willingness to give facts more weight than beliefs and adages. And the belief that we continue to hear -- not just from the pro-Brett Favre crowd, but from pretty much any team with a good running back and shaky quarterback situation -- is that a good passing game will help the running game. The argument of eight-in-the-box versus seven-in-the-box and a good passer "opening up running lanes" is posited by amateurs and professionals alike.
Problem is, the numbers don't seem to bear it out.
If Peter's principle (heh) were true, we'd expect that good passing numbers would result in high average rushing gain. As I pointed out a while back, that's not the case, at least using the stats from the 2008 season.
Pass Total/Run Average Correlation: -0.0956
Correlation, if you'll recall, is always between -1 and 1. The closer you are to 1, the closer the relationship between the two sets of data. A positive correlation (0 to 1) indicates a positive relationship, while a negative correlation (-1 to 0) indicates a negative relationship.
Even with the slight negative correlation, the absolute value of the correlation -- less than 0.1 -- is insignificant enough to be practically meaningless. Thus, according to the 2008 data, there is virtually no correlation between total passing yards and rushing average. A strong passing game does not help out the running game.
But raw passing yards (minus sacks) isn't the only measure of a team's success in passing. Just throwing for a bunch of yards doesn't necessarily make you a good pasisng team. What about the various rate stats?
Passer Rating/Run Average Correlation: -0.105
Adusted Net Yards Per Attempt/Run Average Correlation: -0.010
Again, both results are inconclusive, and it would be harder to have less of a correlation than the ANYA/Run average result (actually -0.00954)! Again, this seems to support the notion that there's no correlation between passing efficiency -- by any measure -- and rushing average.
Of course, I'm still just using one year's worth of data. It takes me a while to compile all the data, so I'll only run a couple more years, 2006 and 2007. The three-year data is presented in the chart below:
|Year||Pass Total/Run Av||Pass Rate/Run Av||ANYA/Run Av|
All three correlations grade out poorly, at least in terms of supporting the theory that passing helps running, and using the fairly small sample size of three seasons. In fact, the original hypothesis -- that a lot of passing yards helps improve a team's average yards per attempt -- seems to have a rather significant negative correlation, meaning that one somewhat implies the opposite of the other (though the direction of the correlation cannot be discerned).
I think this is a case of people trying to sound smarter than they are (like when they say that, despite the glitter and hype of passing games that the way to win is to "run the ball and stop the run") and attributing more importance than is warranted to a "hidden" part of the game. I think it's much simpler than that: Teams that are good at passing pass the ball and so they have better passing numbers than rushing numbers. Teams that are good at running run the ball and so have better rushing numbers than passing numbers. That's it. If it is true that running well opens up the passing game, then the passing numbers will look better and the strong-running team will look more balanced, and vice versa.
In the end, I think that, if you want to be a better running team, improve the parts of your team directly related to your running game: your tailback, fullback, offensive lineman/tight ends/receivers who can run block, etc. Improving the quarterback doesn't really help the running game.
(There is, of course, the question of running back consistency, on a per-carry basis that, without per-carry stats, I can't prove or disprove, but the notion of it strikes me as fishy for two reasons: 1. There's no proof that it will help and it sounds like just another platitude to help us accept the unacceptable; and 2. It's based on the notion that Peterson is that type of "boom-or-bust" running back, which is only prevalent because he played that way in his last two games, while ignoring his previous 28.)
All this doesn't mean that a good quarterback doesn't help a team. I'd be delighted if Drew Brees or Peyton Manning somehow wound up on the Vikings, and it would clearly improve the team, but not because it would make Adrian Peterson look better. But the notion that Brett Favre, or any other quarterback, will make Peterson's life easier is, in my opinion, just another way to make us feel better about accepting ol' #4 as our starting quarterback.