Comments on Advanced NFL Stats: Weekly Roundup

Good, I hoped that the regression formula would be...

2009-01-07T15:16:00.000-05:00

Good, I hoped that the regression formula would be something established from historical data rather than fit to the current data, but you did say it was "mindless" so I wasn't sure. Sorry I didn't read the linked post before commenting.

As for MAE vs. RMSE, of course RMSE will always be greater than or equal to MAE, but if the 8-8 method appears much worse with RMSE then that's an indication of a lot of variance in the magnitude of the errors using that method, since RMSE will punish you for making a few big mistakes. Which would indicate that guessing every team will finish 8-8 is likely to be pretty good most of the time, but you'll probably get a few big mistakes.

No, that doesn't include 2008. It's from 2002-2005...

2009-01-06T13:33:00.000-05:00

No, that doesn't include 2008. It's from 2002-2005, where one season's win totals are used to predict the following season's (a total of 3 "season-pairs").

It's from this post I linked to above. The regression formula is at the bottom of the article.

The 8-8 prediction is clever, but it really depends on how you measure accuracy. Doug chose "w/in 2 games," which is a 5-game spread. If we do mean absolute error, the 8-8 predictions do very well. But we use RMSE (root mean squared error--which is what most statisticians or mathematicians would use), it doesn't hold up well.

We could make 2009 predictions right now that would be as accurate as any that SI or ESPN or FO will make in August. It's not that ours would be very accurate at all, just that nobody's are.

Think about how surprised you would have been to be told in August: Ravens, Dolphins, and Falcons in (avg 3.3 wins in '07). Cowboys, Jaguars, and Patriots out (avg. 13.3 wins).

Who's going to surprise us next year? Rams? Raiders? Chiefs? Lions? Somebody will!

Brian, correct me if I'm wrong but your simple lin...

2009-01-06T13:01:00.000-05:00

Brian, correct me if I'm wrong but your simple linear regression includes intercept and slope values that you solved for after knowing the "'08 wins", right? So that's a fine analysis but it's not a fair predictor, since you know the future already. Or is your mindless regression a generic forumula you always use?

Your point about 8-8 for all teams is a good one.

It seems to me that the odds that all 4 wild card ...

2009-01-05T17:29:00.000-05:00

It seems to me that the odds that all 4 wild card teams are better than their division-winner opponents is simply the odds that the 3rd and 4th best teams in a conference are in the same divisions as the first and second best teams. And that should be 6/14 x 5/13 = 30/182 or about 1 in 6. So it's about 1/36 that all 4 road teams are better on wild-card weekend. Of course, once you throw in HFA, it gets murkier. But the odds still seem pretty reasonable.

R-squared, yes, I can get that. You'll have to for...

2009-01-05T08:46:00.000-05:00

R-squared, yes, I can get that. You'll have to forgive me, I'm not a math whiz...what's the deal with slope? What would that tell me? And how would I find it?

Doug: can you regress your projected wins to actua...

2009-01-04T14:07:00.000-05:00

Doug: can you regress your projected wins to actual wins, finding slope and r-squared?

If I mindlessly regress last year's wins at:
<...

2009-01-04T00:03:00.000-05:00

If I mindlessly regress last year's wins at:

'08 wins = 5.7 + 2.9*('07 wins)

I get 17 teams w/in 2 games. Plus I bet my overall error rate is at least as good as any other prediction.

It literally took me 3 minutes on Excel.

If just guess 8-8 for every team, I get 15 teams w/in 2 games.

Well, I can see your point that it is a waste of t...

2009-01-03T23:23:00.000-05:00

Well, I can see your point that it is a waste of time for game charters or whoever to pour thousands of man hours into analyzing game tape and play-by-play data just to produce a set of projections that a guy like myself can produce in just a couple hours with an Excel spreadsheet. I see what you're saying there. But I don't know that you can say pre-season projections are worthless...I mean, there has to be some value to them. Even if they're just a guide, or course there will be deviations (significant ones at that) but it is pretty amazing to hit 18 teams within 2 games of their actual record before they even play.

That's just it. Your predictions are just as good ...

2009-01-03T22:32:00.000-05:00

That's just it. Your predictions are just as good as any I've seen.

I don't think it's very fair to say that pre-seaso...

2009-01-03T19:55:00.000-05:00

I don't think it's very fair to say that pre-season predictions are worthless. I take a lot of pride in the fact that not only did I put my projections out in March, but that I don't have any amazing statistical formulas or super computers that do the work for me. I take a time-tested stock analysis technique (Relative Strength Index) and apply it to the NFL. Very simple. I just have to determine whether each team is trending downwards toward an RSI of 45 or upward toward an RSI of 55, then make an estimate of a winning percentage that would have them headed in the right direction by the right amount. It's the perfect balance of objectivity and subjectivity if you ask me, and the results are competitive with any other method I've found.

See fo' yo'self:

http://www.thefootballprofessor.com/2008-nfl-forecast/