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

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  • igorkupfer@rogers.com
    ... From: To: Sent: Wednesday, February 05, 2003 10:29 AM Subject: [APBR_analysis] Re: And while I m at it...
    Message 1 of 5 , Feb 5, 2003
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      ----- 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.)
    • dlirag <dlirag@hotmail.com>
      ... rating system -- but it ... accurate, but I can t seem ... a conceptual ... missed shots usually ... be worth -1 with ... know.) Would -0.7 per missed FGA
      Message 2 of 5 , Feb 15, 2003
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        --- 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?
      • Dean Oliver <deano@rawbw.com>
        ... conceptual ... don t ... There s not a lot of solid guidance on what the weights should be. If all you want are better results -- better is a personal
        Message 3 of 5 , Feb 18, 2003
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          --- In APBR_analysis@yahoogroups.com, "dlirag <dlirag@h...>" > 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?

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