tag:blogger.com,1999:blog-38600807.post3302983900380039269..comments2008-01-16T10:45:37.898-05:00Brian Burkenoreply@blogger.comBlogger10125tag:blogger.com,1999:blog-38600807.post-50289564328617984222008-01-16T10:45:00.000-05:002008-01-16T10:45:00.000-05:00

What if wk 1-8 DVOA and wk 9-17 DVOA aren't correlated very highly?I would be fairly shocked if that were true, even for the lousy teams. This is because staying consistent (i.e. having good correlation with later measurements of the same stat) should be true even for stats that are actually poor measures of team strength.Let me give an example. Let's say we believed all the cliches that the

Tarrhttp://www.blogger.com/profile/09242627723328062618noreply@blogger.comtag:blogger.com,1999:blog-38600807.post-60869641213772703732008-01-15T19:47:00.000-05:002008-01-15T19:47:00.000-05:00

I guess I misunderstood your theory.What if wk 1-8 DVOA and wk 9-17 DVOA aren't correlated very highly? The obvious teams would correlate, such as the Pats and Colts, but what about the majority of teams?I think we're thinking along the same lines. One of my next projects is to adjust my model's coefficients in proportion to how noisy they are (after being adjusted for opponent). The other option

Brian Burkehttp://www.blogger.com/profile/12371470711365236987noreply@blogger.comtag:blogger.com,1999:blog-38600807.post-20807045612553721022008-01-15T19:19:00.000-05:002008-01-15T19:19:00.000-05:00

I don't think that analysis would effectively support or detract from my theory. As I understand it, DVOA basically:1) calculates the expected points of down/distance before and after a given play, and2) Normalizes this result against a league-average result at that down/distance.The issue is that the impact on expected points is magnified on third down, simply because third down plays have a

Tarrhttp://www.blogger.com/profile/14368810359650066790noreply@blogger.comtag:blogger.com,1999:blog-38600807.post-68168619084112240262008-01-15T18:51:00.000-05:002008-01-15T18:51:00.000-05:00

Tarr-Factoring in yard line and down and distance is what DVOA really is. I think they try to factor in time remaining and score difference too. So it would be easy enough to test your hypothesis by repeating the longitudinal auto-correlation analysis of Week 1-8 DVOA with Week 9-17 DVOA.

Brian Burkehttp://www.blogger.com/profile/12371470711365236987noreply@blogger.comtag:blogger.com,1999:blog-38600807.post-76733985779986025322008-01-15T17:07:00.000-05:002008-01-15T17:07:00.000-05:00

Very nice analysis. You've made an extremely strong case that considering 3rd down conversion percentage as part of a model based on overall game stats is a bad idea.It would be interesting to see if it holds true if we consider individual play results as oppose to aggregated stats. It's possible that when we consider the context (distance to the marker, and field position) of a given 3rd down,

Tarrhttp://www.blogger.com/profile/09242627723328062618noreply@blogger.comtag:blogger.com,1999:blog-38600807.post-34085206965101453972008-01-14T01:02:00.000-05:002008-01-14T01:02:00.000-05:00

Yes. I'll post how various stats can predict other stats in a future post.

Brian Burkehttp://www.blogger.com/profile/12371470711365236987noreply@blogger.comtag:blogger.com,1999:blog-38600807.post-52413808232211810502008-01-12T13:59:00.000-05:002008-01-12T13:59:00.000-05:00

It's actually adjusted r-squared, which corrects for the number of added variables.

Brian Burkehttp://www.blogger.com/profile/12371470711365236987noreply@blogger.comtag:blogger.com,1999:blog-38600807.post-59889963714707019302008-01-12T13:14:00.000-05:002008-01-12T13:14:00.000-05:00

Are you using OLS for these regressions? Adding a variable should never decrease the R-squared.

Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-38600807.post-53793703117490621362008-01-12T11:53:00.000-05:002008-01-12T11:53:00.000-05:00

Nice article, apparently 3D conversion is just too noisy to be used as a predictor for anything, including itself. Are other stats better predicted without reference to themselves?

mathphystonoreply@blogger.comtag:blogger.com,1999:blog-38600807.post-37239185469860560302008-01-12T11:50:00.000-05:002008-01-12T11:50:00.000-05:00

Have you considered looking at the first down to third down ratio?Maybe something like 1d/3da or 1d - 3d failure.Those would corrolate better with points.They would include first downs made on downs 1 and 2.also yards per third down attempts or yards per third down failures would corrallate pretty well with points.

coldbikemessengernoreply@blogger.com