----- Original Message -----

From: <deano@...>

To: <APBR_analysis@yahoogroups.com>

Sent: Wednesday, February 05, 2003 10:29 AM

Subject: [APBR_analysis] Re: And while I'm at it...

> Ed --

>

> Take a look back at Message 14. That message discusses some of the

> other methods for weighting stats. JohnH of this group wrote a book

> with different weights. There is an economist named Dave Berri who

> also has something effectively similar. There are a few more on the

> web, too. I've developed a matrix showing the relative weights that

> the developers put on the different stats. I can't put that matrix

> out here since it's in the book I've got coming out.

>

Hmm, mostly 0.5 - 1.0, which is what I guessed.

> Yours is slightly different, of course, because you don't include any

> defensive stats, making it purely an offensive tool. That makes it

> somewhat unique.

>

I focus only on offense (and only part of the offense, for that matter) because I'm

incapable of developing an all-encompassing system. I prefer to let you guys slug out a

more comprehensive model -- I've seen how difficult it is. I'll focus on the small

stuff.

I think what makes it different than the others is it's theoretical basis. Most of the

methods you describe are linear weights-type systems, the

add-the-good-subtract-the-bad-to-arrive-at-a-rating models. Mine is a little different.

(First of all, I wanted it to look like a player's points total for a game, so you

would have an easy way of grasping what the rating means.) I assume those other ratings

used some kind of regression to arrive at weights that would produce results that jibe

with a qualitative assessment of player ability. I don't do that (I share your distaste

with linear weights). I only add and subtract stuff with regards to a teams expected

points per possession: Teams can expect 1 point per possession. If a player misses a

shot, he cost the team 1 point. If he turns the ball over, he cost the team 1 point.

Like I said, it's a pretty shaky basis on which to construct a rating system -- but it

seems to produce half decent results. I'd like it to be more accurate, but I can't seem

to do that without changing weights. I'm thinking that there may be a conceptual

problem with my approach that I'm overlooking. (Here's one: since missed shots usually

result in an offensive board 30% of the time, they can't possibly be worth -1 with

regards to a possession. But why does -1 give good results? I don't know.)- --- In APBR_analysis@yahoogroups.com, <igorkupfer@r...> wrote:

> Like I said, it's a pretty shaky basis on which to construct a

rating system -- but it

> seems to produce half decent results. I'd like it to be more

accurate, but I can't seem

> to do that without changing weights. I'm thinking that there may be

a conceptual

> problem with my approach that I'm overlooking. (Here's one: since

missed shots usually

> result in an offensive board 30% of the time, they can't possibly

be worth -1 with

> regards to a possession. But why does -1 give good results? I don't

know.)

Would -0.7 per missed FGA give better results? - --- In APBR_analysis@yahoogroups.com, "dlirag <dlirag@h...>" > a

conceptual> > problem with my approach that I'm overlooking. (Here's one: since

don't

> missed shots usually

> > result in an offensive board 30% of the time, they can't possibly

> be worth -1 with

> > regards to a possession. But why does -1 give good results? I

> know.)

There's not a lot of solid guidance on what the weights should be.

>

> Would -0.7 per missed FGA give better results?

If all you want are better results -- "better" is a personal

decision, so you can try it and see whether the results

are "better". Whether you also account for some teams rebounding

only 20% of their misses and other teams rebounding close to 40% is a

question. And if you modify the weight on missed FGA, should you

also modify the weight on offensive rebounds?

DeanO