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Re: [APBR_analysis] Re: Tendex rating

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  • Michael K. Tamada
    ... [...] ... I think the word you re looking for is epicycles . Unless you re looking for the more general term of adding more and more little adjustments
    Message 1 of 6 , Nov 3, 2001
      On Fri, 2 Nov 2001, Dean Oliver wrote:

      > Model analysis can be evaluated on 3 (or 4) philosophies:
      >
      > 1. Simplicity
      > 2. Reality
      > 3. Conservatism
      > (4. Consistency)

      [...]

      >#2. My favorite example is that people used to think that orbital
      >physics was all built on circles. The sun went around the earth in a
      >big circle. If it wasn't just a circle, it was circles within
      >circles. There was a good name for all of this that fails me right
      >now and I know someone out there can spell this out better. People

      I think the word you're looking for is "epicycles". Unless you're looking
      for the more general term of "adding more and more little adjustments to
      the model to make it fit reality, so much so that the model starts falling
      apart under its own complexity". Thomas Kuhn (referred to in Stuart
      McKibbin's posting) might've had a word for this too, but I forget. When
      the old model gets pushed aside by a new different one, that's a "paradigm
      shift".

      Hey didn't you go to Caltech and shouldn't you know this stuff? ;) But
      you did nail the correct answer to the ellipse modeller: Kepler.

      [...]

      > What's the 3rd thing? Well, conservativeness is important when using
      > a model to set policy (something I do at work). Say you're
      > interested in only the good defensive players in the league (for some
      > reason) and you want your stat to get those guys. Well, you want to
      > make sure you don't get the mediocre ones. Your statistic should
      > come out and there should be no argument that the method you chose is
      > only going to get good defensive players. Not sure it matters much
      > for basketball, except if you're helping the league to rewrite rules.

      I'm not sure about this one. Because an overly "conservative" list of
      good defensive players will STILL get arguments -- from people who
      complain that the list left out players X, Y, and Z, who are great
      defenders.

      It's analogous to statistics: you can be "conservative" and minimize the
      probability of a Type I error by choosing a small significance level. But
      in doing so, you are automatically raising the probability of a Type II
      error.

      A list of "great defenders" which is conservative will avoid Type I
      errors, but will be making more Type II errors.

      Decision theory tells us we should look at the relative cost of Type I
      errors and Type II errors and choose a signficance level which balances
      out the likely errors so as to minimize the costs.

      In other words, sometimes we want a "conservative" list of great
      defenders, but other times a not so conservative one. Depending on the
      purpose of the list.

      > I frankly hate the 4th one. A lot of times, someone has done
      > something stupid before, but because of "consistency", we have to do
      > the same stupid thing again.

      Well there's another kind of consistency, one which is a good thing to
      have: logical self-consistency. E.g. rating systems should avoid
      double-counting (unless there is a reason to put a heavy weight on that
      variable).


      --MKT
    • Mike Goodman
      ... David Robinson is probably a great person, as well as a colossal figure in the history of the game. But: He left a clue to his attitude in an interview I
      Message 2 of 6 , Nov 3, 2001
        --- In APBR_analysis@y..., "Dean Oliver" <deano@t...> wrote:
        .........
        > Hmm, one of the more controversial subjects here, I think, is the
        > Admiral. I heard more complaints about him being in the NBA Top 50
        > than about anyone else. No killer instinct, they said.
        >

        David Robinson is probably a great person, as well as a colossal
        figure in the history of the game.
        But:
        He left a clue to his attitude in an interview I saw some years ago.
        Invoking his Christian ideals, he said his faith in God elevates his
        game; and that (quoting from memory) "when going up against an
        Olajuwon or a Robert Horry, I feel like David against Goliath..."
        Eh?
        In other words, he doesn't feel physically superior to Robert Horry?

        > How has the Admiral performed in the playoffs relative to the
        regular
        > season, then relative to other people? Has he fallen off much more
        > than others in the playoffs? .......


        Per-36-minute standardized equivalents for David Robinson, career

        Games Min. Pct. Sco. Reb. Ast PF Stl TO Blk Total
        Regular 845 35.8 .570 26.5 11.7 2.8 3.1 1.5 2.7 3.3 45.7
        Playoff 96 37.5 .532 22.8 12.2 2.8 3.4 1.4 2.6 2.9 41.8

        The ratio of this playoff rate to regular season rate is .915.
        The "average" playoff rate is around .940 (for 515 alltime players).

        > Mike -- this statement:
        >
        > > What makes David over-the-hill is that he cannot produce at that
        > high
        > > rate for as many minutes as before.
        >
        > The implication is that people can be as good, as efficient as they
        > get older, but just not as long. Was his "rate" (per minute) as
        high
        > before as it is now? Any sense for how this goes down with age
        > relative to minutes played?
        >
        > Dean Oliver
        > Journal of Basketball Studies

        It depends on the player, the team situation, and the coach. Popovich
        may be "babying" DRob by using him only 30 mpg, but it has been
        several years now since he has had back problems and other ailments.
        Jordan seems willing to go 40 minutes at age 38, but that is just
        another chapter-in-the-making of a unique case.
        Per-minute rates are down for any player past his prime. The more
        involved issue is : how to get the most production. Over the course
        of a whole season (playoffs particularly), and over the course of a
        career.
      • Dean Oliver
        ... stuff? ;) But ... Hey, going to Caltech means I know the formulas, how to derive them from first principles, what all the little math symbols mean, and
        Message 3 of 6 , Nov 3, 2001
          --- In APBR_analysis@y..., "Michael K. Tamada" <tamada@o...> wrote:
          >
          > Hey didn't you go to Caltech and shouldn't you know this
          stuff? ;) But
          > you did nail the correct answer to the ellipse modeller: Kepler.
          >

          Hey, going to Caltech means I know the formulas, how to derive them
          from first principles, what all the little math symbols mean, and how
          to go 40 hours without sleeping. It doesn't mean I know the names of
          the famous dead guys. Heck, by going to Caltech, I have a right to
          forget names.

          >
          > I'm not sure about this one. Because an overly "conservative" list
          of
          > good defensive players will STILL get arguments -- from people who
          > complain that the list left out players X, Y, and Z, who are great
          > defenders.
          >
          > It's analogous to statistics: you can be "conservative" and
          minimize the
          > probability of a Type I error by choosing a small significance
          level. But
          > in doing so, you are automatically raising the probability of a
          Type II
          > error.
          >

          This is pretty much my point. In policy making, a policy maker
          really wants to reduce one of those types of errors. Usually the
          policy makers don't care about the cost-benefit of Type I vs. Type II
          errors. Their job is minimize one type and fight with everyone else
          who wants to minimize the other type.

          Not sure how that relates to any hoops stuff we're doing right now,
          but it might in the future, when we start using all those funky math
          symbols.

          > Well there's another kind of consistency, one which is a good thing
          to
          > have: logical self-consistency. E.g. rating systems should avoid
          > double-counting (unless there is a reason to put a heavy weight on
          that
          > variable).

          That's true and a good . I can add that to the routine speech I give
          at work. Then when my people look at me funny, I can blame it on you.

          I would phrase what you're talking about a little differently here,
          though. A method makes assumptions at the start and those
          assumptions should remain true at the end. Thinking off the top of
          my head -- if Tendex assumes all those things to be worth one point,
          shouldn't they all be worth one point at the end, too? Does this
          mean Tendex should add up to points scored?

          I know all the arguments pro and con with Tendex. I always point out
          that Tendex, when applied to teams has only about a 70-80%
          correlation with winning percentage. Which means it's not terribly
          reliable for predicting winning teams and probably no more reliable
          for predicting winning players. I also don't like the fact that it
          really just encourages a lot of shooting. I don't know how well
          Tendex correlates with points scored. But unlike baseball, where
          position players are pretty much responsible for offense and pitchers
          for defense, basketball players are responsible for both. That's why
          I try to keep offensive and defensive contributions separate for
          individuals. Doug Steele has an offensive and defensive Tendex
          rating based on some conversations we had in '94. It was a start.

          DeanO
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