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Re: Tendex rating

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  • Mike Goodman
    Bob, you raise a good many interesting points. While Tendex-like rating systems can t clearly rank such elements as teamwork, chemistry, etc, they seem to
    Message 1 of 6 , Nov 1, 2001
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      Bob, you raise a good many interesting points. While "Tendex-like"
      rating systems can't clearly rank such elements as teamwork,
      chemistry, etc, they seem to well enough measure "scoring
      ability", "rebounding strength", and other qualities that fans and
      coaches would like to know about.

      --- In APBR_analysis@y..., bchaikin@a... wrote:
      > i happen to like the Tendex rating, or - as it has also been
      called - a
      > performance rating or production rating - for exactly what it
      measures,
      > production.

      To split hairs for a moment: I usually think of per-game rates
      as "production", and per-minute rates as "productivity".

      >many people have tried to come up with a single number that
      > measures overall player ability, and i feel this rating is the
      closest to
      > doing just that - while also still being simple enough to calculate
      (so any
      > fan can do it) and by using all of the stats that are readily
      available to
      > fans.

      That is also a criterion of mine. Using traditional, recorded
      quantities not only makes for universal availability, it minimizes
      the number of columns necessary in a player's statistical profile.

      >linear weights can be used to fine tune the formula, but it would
      need
      > to be adjusted every year and would lok like mumbo-jumbo to most
      fans -
      > keeping it simple makes it available to everyone while i believe
      not skimping
      > on accuracy...
      >

      There is much to be done in the fine-tuning area. Adjustment for
      game pace is essential, in my book. Hybridizing the per-minute and
      per-game rates makes one list out of two, another simplification.

      > first off - what it is not. tendex (pts + reb+ ast + st + bs- to -
      pf -
      > missedFT - missedFG) is obviously not an overall rating of player
      ability,
      > for the simply reason that it does not measure a player's defensive
      ability
      > other than ST and BS, and that is certainly a major part of the
      game that the
      > formula is missing....
      >

      One theory is that the "unrecorded" defensive contributions that make
      a player more valuable than his stats show, are part of his overall
      game that makes the coach keep him in the game longer. Thus
      this "unsung" contributor gets more minutes than his counterpart who
      racks up numbers quickly. Minutes-played leads to more statistical
      contributions.

      > BS and ST are the only statistical parameters of "defense" widely
      available
      > today for individual players, and everyone knows that they do not
      necessarily
      > measure overall player defense
      .........
      > since 1977-78 (when TOs were first kept as a stat by the NBA) there
      have been
      > 1096316 fouls called and 985368 FTM. since FTM only result from a
      foul being
      > called, each foul leads to approximately 9/10 of a point being
      scored by the
      > opposition. its actually a little more because some of those one
      million plus
      > fouls called were offensive fouls, so a good approximation is that
      a PF
      > called is worth approximately one point to the opposition. often
      there are
      > times when it is good to foul, but overall this scenario holds
      water.

      I have to differ with this view. A possession is worth, on average,
      1 point. A possession when fouled is worth 1 point. So, fouling
      your opponent, on average, does not increase his odds of scoring.
      The average points per possession are equal. A foul is a neutral act.

      > and
      > since a TO is a loss of team possession, and a team possession is
      worth
      > approximately one point, a TO is worth a loss of one point...
      >
      > obviously a missed FT is a missed opportunity for one point, and a
      missed FG
      > is a loss of ball possession (getting an OFF REB after a missed FG
      simply
      > starts this cycle again). thus PF and TO and missed FT and missed
      FG can each
      > be shown to be approximated as a loss of a single point...
      >
      > OFF REBs regain a possession, and a DEF REB is a gain of ball
      possession.
      > since a player cannot get an AST and a FGM at the same time, and an
      AST leads
      > to a score, it can be shown to be worth approximately one point....
      >

      I confess to a bias toward good passing: in individuals and in
      teams. I like a Celtics team ('80s) where every shot is a good shot,
      because of good ball movement; and I like a Jazz team with a premier
      set-up player.
      However, crediting both the scorer and the assister may give too much
      credit to the team, for a single FG. Not sure how to reconcile this.

      > consequently Tendex is a rating of production and not overall
      player ability,
      > i.e. what a player produces statistically (for those parameters
      measured) for
      > his team. each stat has been shown to have a value close to one
      point...

      I have seen blocks getting more credit (for every block, there is one
      or more "altered" shots, etc.).

      > if you look at the Tendex per minute ratings of players since the
      77-78
      > season, i doubt anyone can argue that those players with the
      highest ratings
      > are indeed true superstars. only very rarely has a player gotten a
      very high
      > rating with doubt cast on his value to his team - aka "no D" kiki
      vandeweghe
      > on the 83-84 nuggets had a 0.685 Tendex/min rating on a team that
      scored 124
      > pts/game while giving up 125. but he did score over 29 pts/g and
      shoot close
      > to 56% and play full time and thus his production was quite high...
      >

      125 ppg is about 125% of the historic average of team scoring. So
      dividing Kiki's scoring rate by 1.25 would give you his projected
      scoring rate on a historically-average team. That is quite a large
      factor, and one I readily employ.

      > Tendex leaves alot to be desired if you're looking for a single
      number to
      > rate overall player ability, but as a measure of player production,
      it is
      > probably the perfect parameter to use since it incorporates all
      available
      > stats. last year teammates kobe bryant and shaquille o'neal scored
      28-29
      > pts/g each, but o'neal's tendex/min rating was a whopping 30%
      greater (.697
      > to .539) showing his true production to the team compared to
      bryant. if
      > bryant was a significantly better defender than o'neal that could
      offset this
      > huge difference, but in fact both are excellent defenders...
      >

      I ranked Shaq about 25% more productive than Kobe, and far ahead of
      the rest of the league, as well.

      > allen iverson (.481 tendex/min) may have led the league in scoring
      last
      > season, but his overall production was only similar to players such
      as paul
      > pierce, glenn robinson, stephon marbury, and (surprise) andre
      miller - his
      > high scoring being "negated" by his poor shooting (same with jerry
      stackhouse
      > - .458).

      Here again, Iverson's scoring rate, while playing for one of the
      league's premier defensive teams, is undervalued unless you factor in
      the team PPG allowed. This may artificially apply his team's defense
      to his individual offense, but it does somewhat justify his MVP
      selection.

      > for those thinking david robinson is over the hill, the spurs led
      > the league in wins last year not just because of duncan (.592
      tendex/min -
      > 5th best in the league) but also because of the admiral (.573 - 8th
      best in
      > the league despite scoring just 14 pts/g) - two players in the same
      starting
      > lineup with 2 of the top 8 tendex/min ratings in the league...
      >
      > bob chaikin
      > bchaikin@b...

      Admiral ranked #13 in my hybridized per-game/per-minute rankings.
      This is lower than the per-minute rank, and higher than the per-game
      rating.
      What makes David over-the-hill is that he cannot produce at that high
      rate for as many minutes as before. (Note, I said over-the-hill, not
      washed-up.)
    • Dean Oliver
      ... calculate ... Model analysis can be evaluated on 3 (or 4) philosophies: 1. Simplicity 2. Reality 3. Conservatism (4. Consistency) Every model that we
      Message 2 of 6 , Nov 2, 2001
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        --- In APBR_analysis@y..., "Mike Goodman" <msg_53@h...> wrote:
        > >many people have tried to come up with a single number that
        > > measures overall player ability, and i feel this rating is the
        > closest to
        > > doing just that - while also still being simple enough to
        calculate
        > (so any
        > > fan can do it) and by using all of the stats that are readily
        > available to
        > > fans.
        >
        > That is also a criterion of mine. Using traditional, recorded
        > quantities not only makes for universal availability, it minimizes
        > the number of columns necessary in a player's statistical profile.
        >

        Model analysis can be evaluated on 3 (or 4) philosophies:

        1. Simplicity
        2. Reality
        3. Conservatism
        (4. Consistency)

        Every model that we use is based upon a compromise between #1 and
        #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
        tried to model what they saw in the sky based on circular orbits or
        circular orbits within circular orbits. It fit the data pretty well,
        but it got damn complicated. Some dude -- I think it was Kepler --
        came up with the laws of orbital motion that had ellipses. These
        ellipses, after the initial period, where, ohmigod Those aren't as
        easy to use as circles!!! -- people realized that they were much more
        robust, explaining things in a way that was ultimately simpler. Then
        (I feel horrible for not remembering this stuff better), we got
        gravity and gravity predicted the elliptical orbits. We got real!
        It all fit together. A model that was not as simple at the start as
        big circles, but ultimately explained a lot more fairly simply.

        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 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.

        My point, which is probably lost through all that rhetoric, is that
        Tendex is simple, but may not be realistic. whatever realistic is.
        Tendex has nothing it can be compared to in order to say if it's
        realistic. It is only a rating. It reflects not points scored nor
        allowed. If it reflects production, no one knows how to ground truth
        it. Tendex and the like are just numerical values reflecting
        approximate ratings. They work pretty well in doing trade value.
        GMs seem to qualitatively use them when doing trades or signing
        players. We generally don't see too many trades of high "production"
        players for low "production" players (except in sign-and-trade deals
        now). People get burned a lot relying on tendex, of course. Vin
        Baker was never ever worth what Seattle paid for him, yet his Tendex
        was quite high. Antawn Jamison is another with a high Tendex (and,
        now, a high salary), but no established effectiveness for winning
        and, more and more, a history that suggests his future won't be too
        great. But the "simplest" model says that he's pretty good.

        The other thing I'd say is what Bill James always said -- most of the
        time you're doing an analysis, you don't care about overall quality,
        you care about one specific thing. Can they rebound? Can they
        score? Can they play defense? Do their skills fit our needs?

        > > for those thinking david robinson is over the hill, the spurs led
        > > the league in wins last year not just because of duncan (.592
        > tendex/min -
        > > 5th best in the league) but also because of the admiral (.573 -
        8th
        > best in
        > > the league despite scoring just 14 pts/g) - two players in the
        same
        > starting
        > > lineup with 2 of the top 8 tendex/min ratings in the league...
        > >
        > > bob chaikin
        > > bchaikin@b...
        >
        > Admiral ranked #13 in my hybridized per-game/per-minute rankings.
        > This is lower than the per-minute rank, and higher than the per-
        game
        > rating.
        > What makes David over-the-hill is that he cannot produce at that
        high
        > rate for as many minutes as before. (Note, I said over-the-hill,
        not
        > washed-up.)

        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. Not a
        champion, they said. But the numbers have been great. He didn't
        have the supporting cast. Once he got a supporting cast, that cast
        was Duncan and who supported who?

        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? He looked absolutely horrible vs. the
        Lakers last year.

        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
      • 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 3 of 6 , Nov 3, 2001
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          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 4 of 6 , Nov 3, 2001
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            --- 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 5 of 6 , Nov 3, 2001
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              --- 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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