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3306Re: My version of WINVAL (my analysis of it)

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  • dan_t_rosenbaum
    Mar 4, 2004
      I probably think of this a little differently. Let's think of three
      kinds of contributions that a player might make to winning.

      1. Measured statistics, i.e. points, rebounds, assists, etc.
      - These measured statistics are the grist of most statistical
      measures of player quality.

      2. Unmeasured contributions to winning that occur during a given
      block of a game
      - This is what the WINVAL play-by-play method is ideal at
      measuring. It picks up things like good entry passes that don't
      lead to assists, good hands that keep a bad pass from being a
      turnover for the passer, a good pick, not spreading the floor
      effectively, checking a guy on defense, providing good help defense,
      disrupting a passer so that he misses an open cutter, etc.

      3. Unmeasured contributions to winning that occur outside a block of
      a game
      - For the most part, WINVAL misses these. This would include fouls
      picked up in one block of a game that make a player more tentative
      in another part of the game, offensive or defensive plays during one
      block of game that have effects on later blocks of the game, team
      cancers or team leaders that affect the effort level of players in
      games and practices (these cancers and leaders may not even play),

      When I referred to "externalities," I probably was thinking of some
      combination of those contributions in categories two and three.

      In my opinion, talent is involved in the first two categories and
      possibly in the third as well, so it is misleading to think of
      WINVAL as mostly picking up the effort contributions not picked up
      by the talent contributions inherent in the measured statistics. It
      is a measured versus unmeasured issue, not a talent versus effort

      DeanO also makes a point about interactions between players, citing
      Sam Cassell as an example. WINVAL is not much better than
      traditional statistics at picking this up - at least in the context
      DeanO brings it up. I guess Minnesota could have looked at how
      effective Cassell was in cases where he was surrounded by
      Milwaukee's best defenders. But this is tough, and I bet this would
      not be very helpful in extrapolating exactly how Cassell would
      perform in the situation he is now in with Minnesota or how he would
      do with Charlotte next season (although that may be a lot like

      So some of these interactions are almost a fourth consideration
      separate from the three kinds of contributions that I outline

      --- In APBR_analysis@yahoogroups.com, "Dean Oliver" <deano@r...>
      > I've been thinking about this statement a bit. Inherently, these
      > play-by-play data do feature all the interactions of a player.
      > do have "externalities." In general, we think that it's good to
      > capture more and not less, but I guess the reason that there is so
      > much noise is that all those externalities really add it.
      > all that information can be hiding true "talent" by capturing also:
      > - decisions to go to a certain player in the offense
      > - system, such as man or zone defense
      > - decisions on what man covers who
      > I'm sure there are other things, but I note that these are actually
      > very important in making translations to other teams. These are,
      > the lineups themselves, very collinear. The defense of Sam Cassell
      > looked a lot worse in Milwaukee than in Minnesota where he has an
      > effective zone to protect him. Minnesota couldn't have seen that
      > really with these stats until it actually put him in a zone. How
      > would Sam do as the first option in an offense? He's not been
      > so if the Bobcats pick him up in the expansion draft (doubtful, of
      > course), would he be able to do that? Or, how would Flip Murray be
      > defensively if the Sonics didn't play their trap all the time?
      > The belief of how important these factors are in performance then
      > matters. If you believe that talent is 99% of the game, the
      > externalities don't matter much. But just the fact that there is a
      > fair amount of noise in the estimates helps support my idea that
      > do matter (even with the new season of data that Dan has). It's
      > putting a number on it, but I tend to go with 70% of performance is
      > talent.
      > DeanO
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