gaucho":2yrgw4c5 said:
Good stuff! A few comments:
1) The body clock effect is real. Therefore, there's no way the guy can "disprove" it by looking at 15 different years. I haven't looked at his data (I will) but really don't need to, the effect will be there. It's possible that in that era with no salary cap and thus more sustained success for given teams, that there is a correlation between location and win percentage. That's easy to control for, and once I do we will see the effect. I promise.
2) I like his idea of using something other than record to measure "expected" win percentage, but year end DVOA numbers is laughable. Those numbers are based on what happened that year. You can't go back and say that based on these year end numbers, there is no body clock effect (i.e. the team that "should have won" did) because you are basing your expectation in those games on the results of those games. Ass backwards.
3) I'm secretly super amused by the axis truncation thing. I think someone on here called it people wanting to flaunt the size of their statistical dong (which is hilarious!). A bunch of people (not you, Popeye) took a first year stats class, or read a famous book from the 50's and want to discredit my results based on one "fact" that they remember. A few comments here:
I don't think anyone on any forum has actually misinterpreted the data based on the graph. Instead, everyone is just scared that someone else will (but nobody does).
There was zero mention of this when these same graphs that were published in the Journal of Exercise Physiology in February. This national journal has a board of scientists that approve the paper before it is published.
There was zero mention of this when I worked directly with Aaron Schatz tweaking the article, nor by anyone else at FO.
It is not a problem.
And why do the axis-gate folks not have a problem with the temperature graph? Isn't that also truncated? Should I show body temperature values down to 0 degrees F? Isn't that really a truncation as 0 degree F is an arbitrary 0. Should I use Kelvins? The whole thing is ridiculous.
4) Finally (I hope this doesn't read as defensive I really do appreciate the comments) If I wanted to futz with the data for pass drops, I would just change alpha to 10% for the entire article and bam, pass drops are statistically significant. I did not do this. Does body clock effect pass drops? Hell yes it does. How could it not (based on the physiological detriments)? Give me 100 WR's and have them run controlled tests in a lab in the a.m. and p.m. and the results will be clear. However in a game, things like prevent defenses mask this correlation. That's all I'm saying.
:th2thumbs:
Numbered your points to make responss more clear.
1) Yeah, I don't think anyone is claiming that the body clock effect isn't real (or knows enough about it to make a substantive claim). What the guy is claiming is that if it's real or not a meaningful effect from it may not show up in NFL games. I kind of touched on this earlier in my discussion of a hypothetical huge N and the problem big data people run into: statistically significant coefficients of meaningless effect size.
Point taken re: the salary cap era, but I think you should apply the same level of skepticism that you do to null findings as you do to non-null findings. Did the salary cap change the shape of the W/L distribution in any given season, or just how long particular teams stayed at either tail across years? Another counter hypothesis might be that body clock stuff should matter more in prior eras when folks like P.C. weren't adjusting for them, but instead we see the reverse (i.e. welcome to noise

).
2) Agreed that end-of-year DVOA poses an endogeneity problem. I don't think it should do THAT much to your models though, as we're talking a pretty small effect on a few games in a season. The question is if end-of-year DVOA is better or worse than record, and I'm not too sure there's a right answer to that without looking into it. I don't think week-by-week DVOA is a good solution however, as we know that week-by-week DVOA is noisy as hell, particularly at the beginning of the season.
3) I'd be annoyed by axis-gate ( :lol: ) if I were you too, but remember, you've now heard the same thing from many different independent people.
Re: the y on body temperature, the axis is fine as it covers the normal range of human body temperatures (to start the y down at zero would be to suggest that x also applies to a dead person in the snow in Alaska :lol: ). What the commenters over there are saying is the same thing I said before: in the NFL the record range is most years goes from about 2-14 to 14-2, so unless your Y goes from 0-1 its going to make your effects look bigger than they are.
It being a "problem" is of course subjective, but if other statistically literate people are suggesting it's a problem, I think it is a problem, as you are needlessly introducing doubt among the population of people who are must equipped to be convinced.
Re: Nobody misinterpreting it, I think this is a poor argument, as one would have to knowingly misinterpret and still not misinterpret it at the same time. What people are saying, myself included, is that they misinterpreted the effect size until they realized the y was so dramatically truncated, and then they felt deceived.
4) Yeah, you could just engage in a post-hoc change of your alpha, but it would introduce the same doubt as your N does n't seem to be anywhere near small enough to justify that, and the effect size is crazy small.
If (just rough estimations for easy math) you assume 25 completions per game and 4 morning east coast road games per year the effect you've found is that once every other year a pass will be dropped.
Or, put another way, pretending the effect was statistically significant (which it wasn't), you've found that morning AM games dropped Wilson's completion percentage from last year from .6819 to .6812, and we don't even report completion percentage to the 10 thousandths column.
Re: P, the issue is only that you try to excuse away a non-significant alpha at .072 right after merrily accepting an alpha at .044 for turnovers. If you don't want to accept .05 as a dichotomous value I totally get that (i.e. the difference between sig and insig is not itself sig), but the range of acceptability needs to extend both directions from .05 unless you want to introduce doubt about your impartiality. TBF people do this all the time (the "nearly" or "close" or "marginally" significant shuffle), but they really shouldn't, and many more don't.