tag:blogger.com,1999:blog-38600807.post2619684293779947274..comments2008-09-01T11:13:17.614-04:00Brian Burkenoreply@blogger.comBlogger8125tag:blogger.com,1999:blog-38600807.post-54462221074390464602008-09-01T11:13:00.000-04:002008-09-01T11:13:00.000-04:00Thanks. According to what I can tell, DVOA is based almost completely on a system published in the 1988 book <I>Hidden Game of Football</I> (p. 69). The system classifies plays from scrimmage as either a "win" or "failure." The authors picked 4 yards for 1st down and 50% to go for 2nd down apparently intuitively. It appears they were pretty close, but I don't think a 4-yd gain on 1st down is can be considered a win because you've actually become slightly less likely to convert the 1st down. Perhaps the numbers looked different in '88, however.<BR/><BR/>DVOA does this same thing, then adds modifiers called "success points" (or something similar) to account for excess yards above (or below) what would be classified as a success. Then all the success points are adjusted for opponents, then compared across teams and situations to compute the % over average. So it's the success points above or below average, not yardage itself that goes into DVOA. (At least as far as I can understand.)<BR/><BR/>One problem I have with DVOA, and FO in general, is that these formulas and stats are "proprietary," as if they're the formula for Coke or the designs for the stealth bomber. Unless they tell people exactly what they're computing, no one can tell if it's valid or worthwhile.Brian Burkehttp://www.blogger.com/profile/12371470711365236987noreply@blogger.comtag:blogger.com,1999:blog-38600807.post-3506957805374166672008-09-01T03:45:00.000-04:002008-09-01T03:45:00.000-04:00Great post. However, as far as the comment about DVOA, it seems as if this is like comparing apples to oranges. My understanding is that DVOA is a different measure of success. It compares a team's performance in a situation to the average performance across the league (i.e. what do you need to do on down x with y yards to go to perform above average). You're measure of performance (which, IMO is more interesting), is looking at things from a 1st-down perspective. So even if gaining 5 yard on 2nd and 7 doesn't increase expected 1st down rate, it is better than average and in that way it is succesfulAnonymousnoreply@blogger.comtag:blogger.com,1999:blog-38600807.post-87063076563488148572008-08-27T09:15:00.000-04:002008-08-27T09:15:00.000-04:00Unfortunately, there's no publicly available source. You'd have to compile the data yourself from individual gamebooks.Brian Burkehttp://www.blogger.com/profile/12371470711365236987noreply@blogger.comtag:blogger.com,1999:blog-38600807.post-52217733847340849192008-08-27T01:58:00.000-04:002008-08-27T01:58:00.000-04:00Where can one find stats like rushing or passing yards on 1st, 2nd and 3rd down?Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-38600807.post-15850302777135223962008-08-01T14:46:00.000-04:002008-08-01T14:46:00.000-04:00One more clarification regarding Dave's comment--It's not that teams convert 33% of their 3rd and 10s. It's that they convert 33% of all series in which they had a 3rd and 10 at some point in the series. So in some cases teams who fail to convert on 3rd and 10 go on to convert on 4th down.Brian Burkehttp://www.blogger.com/profile/12371470711365236987noreply@blogger.comtag:blogger.com,1999:blog-38600807.post-28558063208842019042008-08-01T14:41:00.000-04:002008-08-01T14:41:00.000-04:00Yes, the 66% conversion rate includes all penalties. It's for every series of downs excluding those for which time ran out. It also includes red zone series. The rates definitely decline close to the end zone. <BR/><BR/>But that could be for at least 2 reasons--a smaller field to defend and the attractiveness of an almost automatic 3 points (or both). Teams likely get cautious throwing the ball knowing that a turnover or sack would almost certainly take away points. The latter effect is especially strong late in close games and would tend to skew the conversion rate.Brian Burkehttp://www.blogger.com/profile/12371470711365236987noreply@blogger.comtag:blogger.com,1999:blog-38600807.post-74126078230170879772008-07-31T23:24:00.000-04:002008-07-31T23:24:00.000-04:00Great stuff as usual Brian.<BR/>Is there a significant difference in these stats as you get close to the goal line? Is it harder to make a first down from the opponents 20 than from your own 20 (for example)? It seems like there would be some effect from having less room, and maybe the defense being more intense because you are about to score.brian mnoreply@blogger.comtag:blogger.com,1999:blog-38600807.post-86619421947588190562008-07-30T19:28:00.000-04:002008-07-30T19:28:00.000-04:00Long time lurker. Cool post. I'm somewhat surprised that teams convert greater than 33% of their third downs with more than 10 yards to go and even around 20% with 15 yards to go. <BR/><BR/>38-40% is about median team 3rd down conversion rate. I'm also curious what the yards to go distribution looks like for each down. <BR/><BR/>Does the 66% include 1st downs that have less than 10 yards due to penalties?dave bnoreply@blogger.com