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Re: Value of Assists

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  • dlirag@hotmail.com
    ... possessions, ... app and ... posession ... points). ... and ... If so, ... Here s a list of some Usenet threads discussing the possible value of assists:
    Message 1 of 19 , Jan 4, 2004
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      --- In APBR_analysis@yahoogroups.com, "Michael Tamada" <tamada@o...>
      wrote:
      > -----Original Message-----
      > From: nick@l... [mailto:nick@l...]
      > Sent: Friday, January 02, 2004 1:08 PM
      >
      > [...excellent summary of the principles deleted]
      >
      > >I took all of the team data from 88-89 - 01-02 and computed
      possessions,
      > >assist/possession (app) and points per possession (ppp).
      > >
      > >I then did a simple linear regression on the relationship between
      app and
      > >ppp and generated the following values:
      > >
      > >PPP = 1.0733* APP + 0.7794
      > >
      > >This sets the marginal value of an assist at 1.07 (changing one
      posession
      > >from 0 to 1 asssits increased the predicted team score by 1.07
      points).
      >
      > Fascinating, I thought that similar research had been done before
      and
      > found a much smaller coefficient. But I may be mis-remembering.
      If so,
      > this is a good start.

      Here's a list of some Usenet threads discussing the possible value of
      assists:

      http://groups.google.com/groups?as_q=value%20regression&as_oq=assist%
      20assists&safe=images&ie=UTF-8&oe=UTF-
      8&as_ugroup=*basketball*&as_scoring=d&lr=&hl=en
    • Franklin X
      The major problem I have with assists, is that I believe it isn t a very good individual statistic. It relies too much upon what another player does with the
      Message 2 of 19 , Jan 4, 2004
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        The major problem I have with assists, is that I believe it isn't a
        very good individual statistic. It relies too much upon what another
        player does with the ball. Jason Kidd could get 15 assists, or 0
        assists, it all depends on whether his teammates make shots.
        Something Mr Kidd has no control over.

        It is similiar to the save category in baseball, a statistic that
        doesn't truly measure the effectiveness of a player.

        Of course passing skill and creating high percentage opportunities
        for your teammates is important, but assists alone does not measure
        this.

        thoughts?

        vr,

        Xei
      • Kevin Pelton
        ... I don t buy this, and here s why. In this column, http://www.hoopsworld.com/article_5259.shtml I took a look at the stickiness of various statistical
        Message 3 of 19 , Jan 5, 2004
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          --- In APBR_analysis@yahoogroups.com, "Franklin X" <xeifrank@y...>
          wrote:
          > The major problem I have with assists, is that I believe it isn't
          > a very good individual statistic. It relies too much upon what
          > another player does with the ball. Jason Kidd could get 15
          > assists, or 0 assists, it all depends on whether his teammates
          > make shots. Something Mr Kidd has no control over.

          I don't buy this, and here's why.

          In this column,
          http://www.hoopsworld.com/article_5259.shtml

          I took a look at the "stickiness" of various statistical skills,
          using players who played at least 500 minutes in the consecutive-
          season pairs of 00/01-01/02 and 01/02-02/03.

          I didn't use assist rate per se; I actually used a rating I invented
          I call "pass" rating -- assists^2/turnovers*minutes -- that still
          tracks assists pretty well. I found 0.889 correlation between the
          player's pass rating in Year 1 and Year 2, which was lower than the
          correlations for rebound rate and block rate but higher than the
          correlations for "shoot" (which combines free-throw and three-point
          percentages) and two-point percentage.

          If assists were really that context-dependent, I don't think we'd
          see this high of a correlation. Too many players change teams, and
          too many teams change players, each season.

          If you look at an extreme -- say, trading Gary Payton from this
          year's Lakers to last year's Nuggets -- obviously there's going to
          be a significant change in his assists. For most moves, I don't
          think the change is going to be significant. After all, Jason Kidd
          has been amongst the league leaders in assists everywhere he's gone,
          as was Mark Jackson, to name two top passers who have moved around.

          I think a better argument against the evaluative power of assists is
          the different roles players play in different offenses. Did Mike
          Bibby become a worse passer when he went from Vancouver to
          Sacramento and lost three assists off his average? No, he just had
          the ball in his hands less. Vice versa for Brad Miller.
        • Franklin X
          Well, assist totals can be similiar from year to year or team to team, just like the saves category in baseball, but it still doesn t do anything about the
          Message 4 of 19 , Jan 5, 2004
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            Well, assist totals can be similiar from year to year or team to
            team, just like the saves category in baseball, but it still doesn't
            do anything about the fact that an assist is completely out of the
            control of the person who gets credit for an assist. Basketball has
            many stats like this, there are too many stats in basketball that are
            dependent on what other people do. I admire those of you who are
            able to study and quantify this stuff... :)

            vr,

            Xei

            --- In APBR_analysis@yahoogroups.com, "Kevin Pelton" <kpelton08@h...>
            wrote:
            > --- In APBR_analysis@yahoogroups.com, "Franklin X" <xeifrank@y...>
            > wrote:
            > > The major problem I have with assists, is that I believe it isn't
            > > a very good individual statistic. It relies too much upon what
            > > another player does with the ball. Jason Kidd could get 15
            > > assists, or 0 assists, it all depends on whether his teammates
            > > make shots. Something Mr Kidd has no control over.
            >
            > I don't buy this, and here's why.
            >
            > In this column,
            > http://www.hoopsworld.com/article_5259.shtml
            >
            > I took a look at the "stickiness" of various statistical skills,
            > using players who played at least 500 minutes in the consecutive-
            > season pairs of 00/01-01/02 and 01/02-02/03.
            >
            > I didn't use assist rate per se; I actually used a rating I
            invented
            > I call "pass" rating -- assists^2/turnovers*minutes -- that still
            > tracks assists pretty well. I found 0.889 correlation between the
            > player's pass rating in Year 1 and Year 2, which was lower than the
            > correlations for rebound rate and block rate but higher than the
            > correlations for "shoot" (which combines free-throw and three-point
            > percentages) and two-point percentage.
            >
            > If assists were really that context-dependent, I don't think we'd
            > see this high of a correlation. Too many players change teams, and
            > too many teams change players, each season.
            >
            > If you look at an extreme -- say, trading Gary Payton from this
            > year's Lakers to last year's Nuggets -- obviously there's going to
            > be a significant change in his assists. For most moves, I don't
            > think the change is going to be significant. After all, Jason Kidd
            > has been amongst the league leaders in assists everywhere he's
            gone,
            > as was Mark Jackson, to name two top passers who have moved around.
            >
            > I think a better argument against the evaluative power of assists
            is
            > the different roles players play in different offenses. Did Mike
            > Bibby become a worse passer when he went from Vancouver to
            > Sacramento and lost three assists off his average? No, he just had
            > the ball in his hands less. Vice versa for Brad Miller.
          • Michael Tamada
            Well, in basketball just about every statistic is dependent upon what a player s teammates do. Even rebounds are harder to get if your teammates fail to block
            Message 5 of 19 , Jan 5, 2004
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              Well, in basketball just about every statistic is dependent
              upon what a player's teammates do. Even rebounds are harder
              to get if your teammates fail to block out the opposing
              rebounders.

              But we're not about to therefore stop tracking rebounds,
              nor are we going to stop tracking assists. Of course, the
              art/science comes in figuring out how to best utilize
              those raw statistics (convert rebounds into rebounds per
              minute -- but that fails to correct for FG% and game pace;
              better is to convert them into rebound percentages; I suspect
              that rebound odds would be best of all).

              Assists are trickier than rebounds because they are indeed
              highly dependent upon the performance of teammates.


              But your question was already answered in NickS's original
              posting, plus one of MikeG's replies:

              1. If the NBA started tracking not just the good passes
              that led to assists, but also the good passes that led to
              missed FGAs and the good passes that led to fouls and FTAs,
              we can then look simply at "good passes" (i.e. assist-worthy
              passes) without worrying about the contaminating impact of
              whether the passer's teammate buried the shot or not.

              2. Unfortunately, we're not in that nice situation. What
              then, to make of assists? NickS's work starts us on the
              road to emprically figuring out the average or typical value
              of an assist (I have to look at the Usenet thread that
              someone cited). The other approach which is more immediately
              useful is what MikeG and others have done: recognize that
              while any one assist is not particularly valuable, what assists
              probably do is provide possible evidence or proxies for a
              playmaker's contributions. Hence MikeG pumps up their value
              because an 8-assist player, compared to a 5-assist player,
              is likely making contributions to the team above and beyond
              those inherent in the 3 assisted baskets.

              The situation is analogous to sabrmetricians trying to measure
              defense. Putouts, assists, and errors by themselves are not
              good ways of evaluating defense. Even the more sophisticated
              techniques such as zone ratings are vulnerable to contamination
              from the performance of a player's teammates (fleet or strong-
              armed centerfielders taking fly balls away from their leftfield
              teammates; slow-releasing second basemen costing shortstops
              some deserved double-plays; etc.).


              But if you're looking for some completely teammate-independent,
              context-independent statistic, no you're not going to find one
              in basketball. You won't find one in baseball either, but
              due to the nature of the game many (not all) of the statistics
              there can be made somewhat context-independent.


              I'd wager that assist statistics for starting point guards
              do show more of what KevinP call "stickiness" than save
              statistics do for closers. In baseball, sabrmetricians
              have the luxury of throwing out the save statistic entirely
              and looking instead at runs prevented or DIPS or whatever.
              In basketball we can't throw out the assist statistic because
              then we'd have nothing (except for turnovers).

              But beware of throwing out the save statistic: to simply
              look at a pitcher's stats (defense independent or otherwise)
              per batter faced is still failling to correct for an important
              teammate- or context-dependent factor: the leverage value of
              the inning. Not all innings or batters faced are created equal.
              A reliever who faces three batters and mows them down in the
              7th inning of a 12-0 ballgame has not made the same contribution
              to victory as one who comes in with runners on the corners
              in the 9th inning of a 3-2 ballgame. Some sabrmetricians are
              starting to take these inning-and-score contexts into account,
              but much work remains to be done.



              --MKT


              -----Original Message-----
              From: Franklin X [mailto:xeifrank@...]
              Sent: Monday, January 05, 2004 3:31 AM


              Well, assist totals can be similiar from year to year or team to
              team, just like the saves category in baseball, but it still doesn't
              do anything about the fact that an assist is completely out of the
              control of the person who gets credit for an assist. Basketball has
              many stats like this, there are too many stats in basketball that are
              dependent on what other people do. I admire those of you who are
              able to study and quantify this stuff... :)

              vr,

              Xei

              --- In APBR_analysis@yahoogroups.com, "Kevin Pelton" <kpelton08@h...>
              wrote:
              > --- In APBR_analysis@yahoogroups.com, "Franklin X" <xeifrank@y...>
              > wrote:
              > > The major problem I have with assists, is that I believe it isn't
              > > a very good individual statistic. It relies too much upon what
              > > another player does with the ball. Jason Kidd could get 15
              > > assists, or 0 assists, it all depends on whether his teammates
              > > make shots. Something Mr Kidd has no control over.
              >
              > I don't buy this, and here's why.
              >
              > In this column,
              > http://www.hoopsworld.com/article_5259.shtml
              >
              > I took a look at the "stickiness" of various statistical skills,
              > using players who played at least 500 minutes in the consecutive-
              > season pairs of 00/01-01/02 and 01/02-02/03.
              >
              > I didn't use assist rate per se; I actually used a rating I
              invented
              > I call "pass" rating -- assists^2/turnovers*minutes -- that still
              > tracks assists pretty well. I found 0.889 correlation between the
              > player's pass rating in Year 1 and Year 2, which was lower than the
              > correlations for rebound rate and block rate but higher than the
              > correlations for "shoot" (which combines free-throw and three-point
              > percentages) and two-point percentage.
              >
              > If assists were really that context-dependent, I don't think we'd
              > see this high of a correlation. Too many players change teams, and
              > too many teams change players, each season.
              >
              > If you look at an extreme -- say, trading Gary Payton from this
              > year's Lakers to last year's Nuggets -- obviously there's going to
              > be a significant change in his assists. For most moves, I don't
              > think the change is going to be significant. After all, Jason Kidd
              > has been amongst the league leaders in assists everywhere he's
              gone,
              > as was Mark Jackson, to name two top passers who have moved around.
              >
              > I think a better argument against the evaluative power of assists
              is
              > the different roles players play in different offenses. Did Mike
              > Bibby become a worse passer when he went from Vancouver to
              > Sacramento and lost three assists off his average? No, he just had
              > the ball in his hands less. Vice versa for Brad Miller.




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            • Franklin X
              Michael, thanks for the thoughtful reply. vr, Xeifrank ... doesn t ... has ... are ... ... ... isn t ... the ... point ... and
              Message 6 of 19 , Jan 5, 2004
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                Michael, thanks for the thoughtful reply.


                vr,

                Xeifrank

                --- In APBR_analysis@yahoogroups.com, "Michael Tamada" <tamada@o...>
                wrote:
                > Well, in basketball just about every statistic is dependent
                > upon what a player's teammates do. Even rebounds are harder
                > to get if your teammates fail to block out the opposing
                > rebounders.
                >
                > But we're not about to therefore stop tracking rebounds,
                > nor are we going to stop tracking assists. Of course, the
                > art/science comes in figuring out how to best utilize
                > those raw statistics (convert rebounds into rebounds per
                > minute -- but that fails to correct for FG% and game pace;
                > better is to convert them into rebound percentages; I suspect
                > that rebound odds would be best of all).
                >
                > Assists are trickier than rebounds because they are indeed
                > highly dependent upon the performance of teammates.
                >
                >
                > But your question was already answered in NickS's original
                > posting, plus one of MikeG's replies:
                >
                > 1. If the NBA started tracking not just the good passes
                > that led to assists, but also the good passes that led to
                > missed FGAs and the good passes that led to fouls and FTAs,
                > we can then look simply at "good passes" (i.e. assist-worthy
                > passes) without worrying about the contaminating impact of
                > whether the passer's teammate buried the shot or not.
                >
                > 2. Unfortunately, we're not in that nice situation. What
                > then, to make of assists? NickS's work starts us on the
                > road to emprically figuring out the average or typical value
                > of an assist (I have to look at the Usenet thread that
                > someone cited). The other approach which is more immediately
                > useful is what MikeG and others have done: recognize that
                > while any one assist is not particularly valuable, what assists
                > probably do is provide possible evidence or proxies for a
                > playmaker's contributions. Hence MikeG pumps up their value
                > because an 8-assist player, compared to a 5-assist player,
                > is likely making contributions to the team above and beyond
                > those inherent in the 3 assisted baskets.
                >
                > The situation is analogous to sabrmetricians trying to measure
                > defense. Putouts, assists, and errors by themselves are not
                > good ways of evaluating defense. Even the more sophisticated
                > techniques such as zone ratings are vulnerable to contamination
                > from the performance of a player's teammates (fleet or strong-
                > armed centerfielders taking fly balls away from their leftfield
                > teammates; slow-releasing second basemen costing shortstops
                > some deserved double-plays; etc.).
                >
                >
                > But if you're looking for some completely teammate-independent,
                > context-independent statistic, no you're not going to find one
                > in basketball. You won't find one in baseball either, but
                > due to the nature of the game many (not all) of the statistics
                > there can be made somewhat context-independent.
                >
                >
                > I'd wager that assist statistics for starting point guards
                > do show more of what KevinP call "stickiness" than save
                > statistics do for closers. In baseball, sabrmetricians
                > have the luxury of throwing out the save statistic entirely
                > and looking instead at runs prevented or DIPS or whatever.
                > In basketball we can't throw out the assist statistic because
                > then we'd have nothing (except for turnovers).
                >
                > But beware of throwing out the save statistic: to simply
                > look at a pitcher's stats (defense independent or otherwise)
                > per batter faced is still failling to correct for an important
                > teammate- or context-dependent factor: the leverage value of
                > the inning. Not all innings or batters faced are created equal.
                > A reliever who faces three batters and mows them down in the
                > 7th inning of a 12-0 ballgame has not made the same contribution
                > to victory as one who comes in with runners on the corners
                > in the 9th inning of a 3-2 ballgame. Some sabrmetricians are
                > starting to take these inning-and-score contexts into account,
                > but much work remains to be done.
                >
                >
                >
                > --MKT
                >
                >
                > -----Original Message-----
                > From: Franklin X [mailto:xeifrank@y...]
                > Sent: Monday, January 05, 2004 3:31 AM
                >
                >
                > Well, assist totals can be similiar from year to year or team to
                > team, just like the saves category in baseball, but it still
                doesn't
                > do anything about the fact that an assist is completely out of the
                > control of the person who gets credit for an assist. Basketball
                has
                > many stats like this, there are too many stats in basketball that
                are
                > dependent on what other people do. I admire those of you who are
                > able to study and quantify this stuff... :)
                >
                > vr,
                >
                > Xei
                >
                > --- In APBR_analysis@yahoogroups.com, "Kevin Pelton"
                <kpelton08@h...>
                > wrote:
                > > --- In APBR_analysis@yahoogroups.com, "Franklin X"
                <xeifrank@y...>
                > > wrote:
                > > > The major problem I have with assists, is that I believe it
                isn't
                > > > a very good individual statistic. It relies too much upon what
                > > > another player does with the ball. Jason Kidd could get 15
                > > > assists, or 0 assists, it all depends on whether his teammates
                > > > make shots. Something Mr Kidd has no control over.
                > >
                > > I don't buy this, and here's why.
                > >
                > > In this column,
                > > http://www.hoopsworld.com/article_5259.shtml
                > >
                > > I took a look at the "stickiness" of various statistical skills,
                > > using players who played at least 500 minutes in the consecutive-
                > > season pairs of 00/01-01/02 and 01/02-02/03.
                > >
                > > I didn't use assist rate per se; I actually used a rating I
                > invented
                > > I call "pass" rating -- assists^2/turnovers*minutes -- that still
                > > tracks assists pretty well. I found 0.889 correlation between the
                > > player's pass rating in Year 1 and Year 2, which was lower than
                the
                > > correlations for rebound rate and block rate but higher than the
                > > correlations for "shoot" (which combines free-throw and three-
                point
                > > percentages) and two-point percentage.
                > >
                > > If assists were really that context-dependent, I don't think we'd
                > > see this high of a correlation. Too many players change teams,
                and
                > > too many teams change players, each season.
                > >
                > > If you look at an extreme -- say, trading Gary Payton from this
                > > year's Lakers to last year's Nuggets -- obviously there's going
                to
                > > be a significant change in his assists. For most moves, I don't
                > > think the change is going to be significant. After all, Jason
                Kidd
                > > has been amongst the league leaders in assists everywhere he's
                > gone,
                > > as was Mark Jackson, to name two top passers who have moved
                around.
                > >
                > > I think a better argument against the evaluative power of assists
                > is
                > > the different roles players play in different offenses. Did Mike
                > > Bibby become a worse passer when he went from Vancouver to
                > > Sacramento and lost three assists off his average? No, he just
                had
                > > the ball in his hands less. Vice versa for Brad Miller.
                >
                >
                >
                >
                > Yahoo! Groups Links
                >
                > To visit your group on the web, go to:
                > http://groups.yahoo.com/group/APBR_analysis/
                >
                > To unsubscribe from this group, send an email to:
                > APBR_analysis-unsubscribe@yahoogroups.com
                >
                > Your use of Yahoo! Groups is subject to:
                > http://docs.yahoo.com/info/terms/
              • bchaikin@aol.com
                But if you re looking for some completely teammate-independent, context-independent statistic, no you re not going to find one in basketball.  you sure about
                Message 7 of 19 , Jan 5, 2004
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                  But if you're looking for some completely teammate-independent, context-independent statistic, no you're not going to find one in basketball. 

                  you sure about this? for the sake of arguement, how could you prove/disprove this?...

                  don't you think free throw shooting is pretty much teammate independent and context independent? what about player's FG%s? do you believe they change only because of varying teammates (obviously not)? if not how can you associate a change in FG% due to varying teammates knowing there are other reasons for it changing?

                  as for assists, again i can show you a number of players (PGs for example) whose ast/min are basically the same as they are traded from team to team, or change slightly to the point of a change being random, and i can also show you examples where its different...

                  on the outside this assumption sounds plausible, but how would you show this to be true using numbers?...

                  bob chaikin
                  bchaikin@...














                • Michael Tamada
                  ... From: bchaikin@aol.com [mailto:bchaikin@aol.com] Sent: Monday, January 05, 2004 11:32 AM To: APBR_analysis@yahoogroups.com Subject: Re: [APBR_analysis] Re:
                  Message 8 of 19 , Jan 5, 2004
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                    -----Original Message-----
                    From: bchaikin@... [mailto:bchaikin@...]
                    Sent: Monday, January 05, 2004 11:32 AM
                    To: APBR_analysis@yahoogroups.com
                    Subject: Re: [APBR_analysis] Re: Value of Assists

                    But if you're looking for some completely teammate-independent, context-independent statistic, no you're not going to find one in basketball. 

                    you sure about this? for the sake of arguement, how could you prove/disprove this?...

                    don't you think free throw shooting is pretty much teammate independent and context independent? what about
                    [Michael Tamada]   Correct, FT% is the one statistic which is truly context independent.
                     
                     player's FG%s? do you believe they change only because of varying teammates (obviously not)? if not how can you associate a change in FG% due to varying teammates knowing there are other reasons for it changing?

                    [Michael Tamada] What are you asking here?  You correctly infer that I am not claiming that changes of teammates are the only thing which cause FG% to change.  There are a lot of things (context)  which cause players' FG% to change. 
                     
                    So what then is your question?  Wilt Chamberlain shot 51% in 1962 while averaging 50 points per game.  In 1973 he set an NBA record by shooting 73% (but he scored only 13 points per game).
                     
                    Nowhere have I claimed that it's solely Wilt's teammates that caused his FG% to rise. 
                     
                    But what I will claim (and this hardly seems controversial) is that Wilt's context changed.  His role on the team changed.  He shot less, and took largely high-percentage shots in 1973 instead of bearing the brunt of the offensive burden as he did in 1962.  (And yes, having Gail Goodrich and Jerry West around also contributed to the change in his stats, but no, it's not that alone which caused Wilt's stats to change.)
                     
                    His skills probably changed also, from 1962 to 1973.  But I don't think anyone would claim that his inherent 
                    marksmanship rose by 22 percentage points (indeed, his FT percentage  FELL from 61% to 51%).  In terms of overall skills (including youthful athleticism) he probably had better scoring ability in 1962 than he did in 1973.  Yet his 1973 FG% was higher.   Why?  Context:  Team role.  Coach's design of the offense.  And yes, teammates too.
                     

                     
                    as for assists, again i can show you a number of players (PGs for example) whose ast/min are basically the same as they are traded from team to team, or change slightly to the point of a change being random, and i can also show you examples where its different...


                    on the outside this assumption sounds plausible, but how would you show this to be true using numbers?...

                    [Michael Tamada] Again, what are you asking for?  A proof that every single player who experiences a change in teammates must show some large change in assists per game, or scoring per game?  No, not every single teammate change is going to result in some huge statistical change.  
                     
                    My point (or more accurately Xei's initial point) is that NOT EVERY TEAMMATE CHANGE IS GOING TO RESULT  IN ASSISTS PER GAME STAYING THE SAME.  Many will cause a player's assist numbers to change.  The Mike Bibby example that KevinP gave is a good one.  Here's another:  what do you think would happen if one of the better young point guards in the league, one sharing a name with a notorious president, suddenly acquired a backcourt partner who's one of the best playmakers in NBA history.  Might it not be reasonable to expect that the presidential point guard's assists will go down?
                     
                    Norm Nixon averaged 9.0 assists per game in 1979.  In 1980, with Magic Johnson around, he got 7.8, and averaged fewer than 8.0 over the four years that he shared a backcourt with Magic. 
                     
                    Trade Nixon from the Lakers to the Clippers, and presto! his assists went to 11.1 per game.  And the 1984 Clippers made a LOT fewer FGs than the 1983 Lakers did.  His assists were still a pre-Magic-esque 8.8 in 1985.  In 1986 injuries took hold and all his offensive numbers declined, and that was the end of his NBA career except for a brief 1989 comeback.
                     
                     
                    If your question is:  does every change in teammates cause a big change in statistics, the answer is no.
                    If your question is:  does every change in teammates cause no change in statistics, the answer is again no.  See Bibby and Nixon.
                     
                     
                    Let me re-quote one of your passages:
                     
                    as for assists, again i can show you a number of players (PGs for example) whose ast/min are basically the same as they are traded from team to team, or change slightly to the point of a change being random, and i can also show you examples where its different...
                    I agree 100%.   Thus I do not understand what your question is.
                     
                     
                     
                    --MKT
                  • Dean Oliver
                    ... are old news. ... volunteers ... or ... assist ... Couple comments (I m on the road and have little time... again)... 1. In my book, I surveyed the
                    Message 9 of 19 , Jan 5, 2004
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                      --- In APBR_analysis@yahoogroups.com, nick@l... wrote:
                      > I just joined this group so apologies if the following throughts
                      are old news.
                      >
                      > > From: "Kevin Pelton" <kpelton08@h...>
                      > > The value of assists? To get a legitimate answer would probably
                      > > require at least a season-long or league-wide study where
                      volunteers
                      > > tracked whether unmade shots would have been credited an assist
                      or
                      > > not. Ask DeanO how difficult that would be.
                      >
                      > I've been trying to think of a good way to measure the value of an
                      assist
                      > since John Hollinger's first prospectus came out.
                      >

                      Couple comments (I'm on the road and have little time... again)...

                      1. In my book, I surveyed the different linear weights methods for
                      the weight they assign to assists relative to points. They all did
                      it different ways, some more scientific than others. That range was
                      actually one of the smaller ones for all stats. The average value
                      was about 1. Not that the average means much in terms of truth.

                      2. If you look at team success as a function of assists, assists
                      mean little. Some good teams have needed assists to be good. Others
                      haven't. It is a style thing.

                      Anyway, I don't try to put a constant point value on assists. If
                      you're looking for a rule of thumb. A point isn't bad, I suppose.

                      DeanO


                      > Here's my current thinking on the subject.
                      >
                      > To get a perfectly accurate number we would need two stats that
                      aren't
                      > currently recorded -- times in which a pass is made that would
                      result
                      > an an assist if a shot was made (potential assists) in which the
                      player
                      > receiving the pass gets fouled and potential assists in which the
                      > player receiving the pass misses the shot.
                      >
                      > The latter is of crucial importance. Imagine a jump shooter who can
                      shoot
                      > 35% if they have to create off the dribble, and 65% if they can
                      catch and
                      > shoot. Then imagine that the team runs 40 plays for the shooter, 20
                      plays
                      > in which he has to create off the dribble (no potential assist),
                      and 20
                      > in which he receives a pass (potential assist). At the end of that
                      sequence
                      > he has shot 20-40 (40 pts) and the pg has racked up 13 assists. If
                      there
                      > were no pg to pass the ball he would shoot 14-40 (28 pts). In this
                      > case the marginal value of an assist is clearly (40-28)/13 or ~ 1
                      pt.
                      >
                      > If we were to just look at the first situation (20-40, 13 assists)
                      and
                      > say "he went 7-27 on shots that were not assisted" we would assume
                      that
                      > his FG% would be 26% without a pg to pass the ball (and 100% when
                      > generating an assist) and would set the value of an assist at 1.48
                      pts. To
                      > get the true value of an assist we need to understand that not every
                      > potential assist results in a basket.
                      >
                      > Lacking any way to compute those percentages directly (if we had
                      the two
                      > stats I mentioned we could compute PSA for situations involving a
                      potential
                      > assist, and PSA for situations not involving an assist) we have to
                      arrive
                      > at the numbers indirectly.
                      >
                      > I decided that it made more sense to look at assists as a team stat
                      rather
                      > than an individual stat. I think this because assists are usually
                      the
                      > result of an offense running properly, and that's a team effort. I
                      also
                      > think that we have to move from the individual to the team level to
                      have a
                      > closed system that includes both the passer and the scorer.
                      >
                      > I took all of the team data from 88-89 - 01-02 and computed
                      possessions,
                      > assist/possession (app) and points per possession (ppp).
                      >
                      > I then did a simple linear regression on the relationship between
                      app and
                      > ppp and generated the following values:
                      >
                      > PPP = 1.0733* APP + 0.7794
                      >
                      > This sets the marginal value of an assist at 1.07 (changing one
                      posession
                      > from 0 to 1 asssits increased the predicted team score by 1.07
                      points).
                      >
                      > This methodology has a couple problems, some intentional some not.
                      It
                      > creates the chicken/ egg problem of whether the correlation between
                      assists
                      > and offense is caused by good offense creating assist
                      oppportunities or
                      > visa versa. Personally I think this question is a little like the
                      question
                      > about do coaches succeed because of talented players or visa versa.
                      Yes a
                      > talented offense makes things easier for players with good passing
                      skills,
                      > but it also takes special skills to play in that offense.
                      >
                      > You could, if you wanted, phrase the question as "did moving from
                      Cleveland
                      > to sactown suddenly make Brad Miller a better player?" My
                      methodology
                      > implies an answer of, "if he is contributing more to the team
                      success now
                      > than he did in cleveland we have to treat him as if he is a better
                      player."
                      > Perhaps he's benefiting from the team, perhaps he has a chance to
                      show
                      > skills that he had all along but couldn't get full benefit from
                      before.
                      >
                      > In addition, I agree with John Hollinger that, intuitively, this
                      seems like
                      > too high a value to place on assists. But I still think it's
                      interesting to
                      > look at the numbers this way and it's the best statistical
                      assessment that
                      > I can think of.
                      >
                      > I'm curious to know what everyone makes of that and if someone
                      wants to run
                      > the calculation on a larger dataset.
                      >
                      > It would also be interesting to look at the differences between pre-
                      1994-95
                      > and post 1994-95, as the number of 3-pointers attempted increased
                      > dramatically that year.
                      >
                      > Comments would be appreciated.
                      >
                      > Nick Scholtz
                    • nick_scholtz
                      Thanks to everyone for your thoughtful responses. I m happy that finding this group got me to organize my thoughts on the subject and I m continuing to go
                      Message 10 of 19 , Jan 5, 2004
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                        Thanks to everyone for your thoughtful responses.

                        I'm happy that finding this group got me to organize my thoughts on
                        the subject and I'm continuing to go through my data (one interesting
                        result: the lockout season had app rates that were far, far below
                        normal).

                        I will say that I am not a statistician (it's been seven years since I
                        last had stats training) so I am hoping that someone with more
                        experience than I could replicate the analysis.

                        Mike T, thanks for your clarity in explaining the fact that the value
                        of an assist is going to represent more than just the value of the
                        single play that results in the assist. Ideally, if my methodology is
                        sound, it should represent the complete real value of passing (as
                        measured by assists) on team offense. That was my hope in chosing to
                        use team stats, and you explained that better than I could have.

                        Kevin P: your examples of Mike Bibby losing assists and Brad Miller
                        gaining assists when being traded to the Kings is exactly why I am
                        interested in team totals rather than individual players. That
                        eliminates distribution of assists as a factor. That was intentional,
                        but it may make it harder to judge the marginal value of assists from
                        a specific position (like PG).


                        Dean Olliver wrote:
                        > 2. If you look at team success as a function of assists, assists
                        > mean little. Some good teams have needed assists to be good.
                        > Others haven't. It is a style thing.

                        Really? I admit I haven't had a chance to read your book yet but this
                        statement seems very suprising to me. As I've said I think an assist
                        almost always means that an offense is functioning well. While an
                        offense can function without generating assists I would be suprised if
                        a good offense would consistantly fail to generate assists.

                        I would be perfectly willing to believe that the number of assists for
                        the team leader in assists doesn't correlate to success but that's
                        different.

                        When I look at my data set (88-89 through 01-02) only 3 of the top 30
                        teams have below average assists/possession. In addition the
                        correlation between app and winning percentage is positive (it looks
                        like an improvement of .001 in assists/possession should generate a
                        .4% increase in win percentage).

                        In general,we know that offensive efficiency correlates to winning. So
                        if assists correlates to offensive efficiecy shouldn't it correlate to
                        winning as well?

                        For the record, the 3 top teams that ranked below average in app are
                        89-90 Trailblazers, 96-97 heat, and 94-95 Spurs. In addition the 88-89
                        Pistons and 99-00 Lakers were essentially average. The only team on
                        the list that suprises me is the Trailblazers but looking at them they
                        got lots of assists from their back-court but very few from anywhere
                        else.

                        Nick Scholtz
                      • bchaikin@aol.com
                        (A) But if you re looking for some completely teammate-independent, context-independent statistic, no you re not going to find one in basketball. (B) you sure
                        Message 11 of 19 , Jan 5, 2004
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                          (A) But if you're looking for some completely teammate-independent, context-independent statistic, no you're not going to find one in basketball.

                          (B) you sure about this? for the sake of arguement, how could you prove/disprove this?don't you think free throw shooting is pretty much teammate independent and context independent? 

                          (A) Correct, FT% is the one statistic which is truly context independent.

                          (B) what about player's FG%s? do you believe they change only because of varying teammates (obviously not)? if not how can you associate a change in FG% due to varying teammates knowing there are other reasons for it changing?

                          (A) What are you asking here?  You correctly infer that I am not claiming that changes of teammates are the only thing which cause FG% to change.  There are a lot of things (context)  which cause players' FG% to change. 

                          i am not asking anything. the above (top) statement was made, as if to be factual. it is in fact an assumption, and an incorrect one. FT% was just the obvious statistic to counter the assumption. i simply stated that - for the sake of arguement - the above assumption, if you believe it to be true, is hard to prove thru stats analysis. if you could prove it to be true, i'd love to see it...

                          just because there are 5 players on a team at one time during a game doesn't mean the variability in the stats is such that there aren't patterns of consistency to be found....

                          (A) So what then is your question? 

                          that if someone indeed believes the above assuption to be true to show how it is true. i can show you many examples of players who change teams (i.e. teammates) but who in fact play pretty much the same - same FG%, same assists per game or per minute, same touches/min, etc. in other words their compilation of statistics appears to be independent of the specific teammates. on the other hand i can also show you players who change dramatically with new or different teammates....

                          (A) Wilt Chamberlain shot 51% in 1962 while averaging 50 points per game.  In 1973 he set an NBA record by shooting 73% (but he scored only 13 points per game).

                          true - some players increase their FG% with decreased FGAs. yet i can easily give you innumerable examples of players who shot less FGA from one year to another and had a worse FG%, and some who shoot the same or close to the same FG% regardless of the number of FGA. this is precisely the point - at times a stat can appear to be dependent, at other times independent...

                          (A) Nowhere have I claimed that it's solely Wilt's teammates that caused his FG% to rise. 

                          a statement was made that "...if you're looking for some completely teammate independent statistic...you're not going to find one in basketball...". on the contrary you will find that (a) FT% is pretty much teammate independent and context independent and that (b) many players shoot pretty much the same FG% regardless of their teammates. that would appear to me to show that in their cases the stat of FG% is indeed teammate independent...

                          there are (were) many players who shot pretty much the same FG% season to season with varying teammates or on different teams. this would appear to show that in their cases that stat is, quote "...teammate independent, context independent...". also for many other players this is not the case...

                          what you will find is that many players, regardless of who their teammates are, still shoot the ball from the same areas on the floor on a regular basis, and consequently shoot about the same FG% from season to season. their minutes per game and/or touches per game may change, resulting in varying pts/g or pts/min, but because they are shooting from the same areas their FG% can resultingly be the same or close to the same on a consistent basis...

                          (A) But what I will claim (and this hardly seems controversial) is that Wilt's context changed.  His role on the team changed.  He shot less, and took largely high-percentage shots in 1973 instead of bearing the brunt of the offensive burden as he did in 1962.  (And yes, having Gail Goodrich and Jerry West around also contributed to the change in his stats, but no, it's not that alone which caused Wilt's stats to change.)

                          (A) His skills probably changed also, from 1962 to 1973.  But I don't think anyone would claim that his inherent marksmanship rose by 22 percentage points (indeed, his FT percentage  FELL from 61% to 51%).  In terms of overall skills (including youthful athleticism) he probably had better scoring ability in 1962 than he did in 1973.  Yet his 1973 FG% was higher.   Why?  Context:  Team role.  Coach's design of the offense.  And yes, teammates too.

                          chamberlain played 14 seasons in the nba. antoine carr played 16 seasons, and he had a career FG% of 50.3%. in 89-90 and 90-91 for the sacramento kings he averaged just under 20 pts/g (19.7) shooting 50.3% from the floor playing 31 min/g. he had different teammates than his other years in the league and his role was different - that of a scorer or a primary scorer (in the 2 seasons with SAC he was the 2nd leading scorer and 1st leading scorer on the team). the rest of his 16 year career he shot 50.3% yet only twice averaged over 10 pts/g....

                          i'm sure his role was different in SAC as with his other teams, yet he shot about the same. for carr there was no correlation between an increase or decrease in FG% with an increase or decrease in FGA. what was different is that his touches/min and min/g game increased because of his different teammates - but his FG% remained the same because he basically shot from the same areas on the floor as he had throughtout his career. so in his case (and many other players) FG% was teammate independent...

                          (B) as for assists, again i can show you a number of players (PGs for example) whose ast/min are basically the same as they are traded from team to team, or change slightly to the point of a change being random, and i can also show you examples where its different...

                          (B) on the outside this (top) assumption sounds plausible, but how would you show this to be true using numbers?...

                          (A) Again, what are you asking for?  A proof that every single player who experiences a change in teammates must show some large change in assists per game, or scoring per game?  No, not every single teammate change is going to result in some huge statistical change. 

                          simply asking that if someone believes the top assumption to be true to show it to be true using statistics...

                          (A) My point (or more accurately Xei's initial point) is that NOT EVERY TEAMMATE CHANGE IS GOING TO RESULT  IN ASSISTS PER GAME STAYING THE SAME.  Many will cause a player's assist numbers to change.  The Mike Bibby example that KevinP gave is a good one.  Here's another:  what do you think would happen if one of the better young point guards in the league, one sharing a name with a notorious president, suddenly acquired a backcourt partner who's one of the best playmakers in NBA history.  Might it not be reasonable to expect that the presidential point guard's assists will go down?

                          the fact is is that how often a player shoots, passes, gets fouled, and turns the ball over per ball possession is indeed pretty much - and for the most part - teammate and context independent, contrary to the assumption made. on the other hand how often a player touches the ball on offense is strongly influenced by his teammates. there are many cases of players truly altering their game (conscience efforts to shoot less, pass more or shoot more, pass less) when going to different teams of with new and or different teammates, but - again - for the most part these attributes are teammate and context independent, absolutely the opposite the assumption made....

                          so in pro basketball there are a number of stats that are for the most part teammate and context independent....

                          (A) Norm Nixon averaged 9.0 assists per game in 1979.  In 1980, with Magic Johnson around, he got 7.8, and averaged fewer than 8.0 over the four years that he shared a backcourt with Magic. 

                          (A) Trade Nixon from the Lakers to the Clippers, and presto! his assists went to 11.1 per game.  And the 1984 Clippers made a LOT fewer FGs than the 1983 Lakers did.  His assists were still a pre-Magic-esque 8.8 in 1985.  In 1986 injuries took hold and all his offensive numbers declined, and that was the end of his NBA career except for a brief 1989 comeback.

                          again this is just one example - i can show you players who regardless of their teammates have pretty much the same ast/min during the majority of their careers. that would tell me that for those players assists are pretty much teammate and context independent...

                          (A) If your question is:  does every change in teammates cause a big change in statistics, the answer is no.
                          If your question is:  does every change in teammates cause no change in statistics, the answer is again no.  See Bibby and Nixon.

                          (A) Let me re-quote one of your passages:

                          (B) as for assists, again i can show you a number of players (PGs for example) whose ast/min are basically the same as they are traded from team to team, or change slightly to the point of a change being random, and i can also show you examples where its different...
                          I agree 100%.  

                          (A) Thus I do not understand what your question is.

                          basketball has a number of stats that are - for many players - teammate and context independent, contrary to your assumption that "appeared" to be stated as factual. since your assumption cleary states there are none in basketball, i simply asked for arguement's sake to show how you arrived at that conclusion, and since this is a stats analysis discussion group, to show how with the stats...

                          bob chaikin
                          bchaikin@...







                        • Dean Oliver
                          ... this ... if ... for ... What the book says (as it s better than my memory): There is a correlation between good passing teams and good offensive teams.
                          Message 12 of 19 , Jan 8, 2004
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                            --- In APBR_analysis@yahoogroups.com, "nick_scholtz" <nick@l...>
                            wrote:
                            >
                            > Dean Olliver wrote:
                            > > 2. If you look at team success as a function of assists, assists
                            > > mean little. Some good teams have needed assists to be good.
                            > > Others haven't. It is a style thing.
                            >
                            > Really? I admit I haven't had a chance to read your book yet but
                            this
                            > statement seems very suprising to me. As I've said I think an assist
                            > almost always means that an offense is functioning well. While an
                            > offense can function without generating assists I would be suprised
                            if
                            > a good offense would consistantly fail to generate assists.
                            >
                            > I would be perfectly willing to believe that the number of assists
                            for
                            > the team leader in assists doesn't correlate to success but that's
                            > different.

                            What the book says (as it's better than my memory):

                            "There is a correlation between good passing teams and good offensive
                            teams. Teams that have a higher percentage of their field goals
                            accompanied by assists tend to be better offensively. It's not an
                            incredibly strong trend, but only five of the top 25 offenses were
                            under the league average in this statistic."

                            Interpret that how you will. My general approach in working with
                            teams is to put assists pretty low on the list of stats to
                            follow/prioritize. It has come up, especially when a team has a
                            single star (it became an issue early this season when Flip Murray
                            got a little too dominant in the Sonic offense). But most teams
                            should care more about making shots and letting assists follow,
                            rather than the other way...


                            DeanO
                          • nick_scholtz
                            ... Interesting. I thought that a year or two ago there was a study done on the Sonics that compared their win/loss records in games when they (1) had more
                            Message 13 of 19 , Jan 8, 2004
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                              --- In APBR_analysis@yahoogroups.com, "Dean Oliver" <deano@r...>
                              wrote:

                              > What the book says (as it's better than my memory):
                              >
                              > "There is a correlation between good passing teams and good
                              > offensive teams. Teams that have a higher percentage of their field
                              > goals accompanied by assists tend to be better offensively. It's
                              > not an incredibly strong trend, but only five of the top 25 offenses
                              > were under the league average in this statistic."
                              >
                              > Interpret that how you will. My general approach in working with
                              > teams is to put assists pretty low on the list of stats to
                              > follow/prioritize. It has come up, especially when a team has a
                              > single star (it became an issue early this season when Flip Murray
                              > got a little too dominant in the Sonic offense). But most teams
                              > should care more about making shots and letting assists follow,
                              > rather than the other way...

                              Interesting. I thought that a year or two ago there was a study done
                              on the Sonics that compared their win/loss records in games when they
                              (1) had more rebounds than their opponent (2) shot more free throws
                              than their opponent (3) had fewer turn overs than their opponent OR
                              (4) had more assists than their opponent.

                              IIRC correctly, assists were by far the best predictor of wins, but
                              that study only covered one team for a third of a season.

                              Perhaps this would be a good study for 82games.com (HINT HINT).

                              BTW, Dean, if you're still on the road, I live in Bellingham WA. I
                              doubt you'll travel this far North, but please send me an e-mail if
                              you're going to be in the area.

                              Nick Scholtz
                            • Stephen Greenwell
                              IIRC correctly, assists were by far the best predictor of wins, but that study only covered one team for a third of a season. This is only a casual
                              Message 14 of 19 , Jan 8, 2004
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                                IIRC correctly, assists were by far the best predictor of wins, but
                                that study only covered one team for a third of a season.

                                This is only a casual observation, but shouldn't assists be most directly related to winning?  That is what I would have expected going into the study.  After all, an assist only occurs on a scored basket; you need to score to win.  The teams that score the most will probably have the most assists.  The other stats, such as rebounds, free throw rate, and turnovers, don't relate directly to points.

                                Steve Greenwell
                              • Kevin Pelton
                                ... http://www.sonicscentral.com/kevin7.html Is that the study you re referring to? I imagine you read it. As I explained in my message to you specifically,
                                Message 15 of 19 , Jan 8, 2004
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                                  --- In APBR_analysis@yahoogroups.com, "nick_scholtz" <nick@l...>
                                  wrote:
                                  > --- In APBR_analysis@yahoogroups.com, "Dean Oliver" <deano@r...>
                                  > wrote:

                                  > Interesting. I thought that a year or two ago there was a study
                                  > done on the Sonics that compared their win/loss records in games
                                  > when they (1) had more rebounds than their opponent (2) shot more
                                  > free throws than their opponent (3) had fewer turn overs than
                                  > their opponent OR (4) had more assists than their opponent.
                                  >
                                  > IIRC correctly, assists were by far the best predictor of wins, but
                                  > that study only covered one team for a third of a season.

                                  http://www.sonicscentral.com/kevin7.html

                                  Is that the study you're referring to? I imagine you read it. As I
                                  explained in my message to you specifically, again the important
                                  distinction is in looking at pure assists (or assists per
                                  possession) as opposed to assists per field goal made. A team with
                                  more assists is almost always going to have more points, which I
                                  hear correlates very strongly with winning.

                                  Just to throw it out there, here are the correlations this year for
                                  the Sonics (i.e. the number of times the team with the better mark
                                  has won the game):

                                  Assists: .844
                                  Ast/FGM: .719

                                  I was pretty surprised to see the latter be so high. And, just for
                                  the record:

                                  FG%: .813
                                  3PT%: .688
                                  Steals: .656
                                  Rebounding percentage: .594
                                  FT%: .594
                                  Turnovers: .500 (surprising)
                                  Blocks: .500
                                • Dean Oliver
                                  ... Historically, FG% and Defensive rebounds have been the best indicators in this kind of study (see chp 6). This kind of study is, well, flawed. Defensive
                                  Message 16 of 19 , Jan 9, 2004
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                                    --- In APBR_analysis@yahoogroups.com, "Kevin Pelton" <kpelton08@h...>
                                    wrote:
                                    > --- In APBR_analysis@yahoogroups.com, "nick_scholtz" <nick@l...>
                                    > wrote:
                                    > > --- In APBR_analysis@yahoogroups.com, "Dean Oliver" <deano@r...>
                                    > > wrote:
                                    >
                                    > > Interesting. I thought that a year or two ago there was a study
                                    > > done on the Sonics that compared their win/loss records in games
                                    > > when they (1) had more rebounds than their opponent (2) shot more
                                    > > free throws than their opponent (3) had fewer turn overs than
                                    > > their opponent OR (4) had more assists than their opponent.
                                    > >
                                    > > IIRC correctly, assists were by far the best predictor of wins, but
                                    > > that study only covered one team for a third of a season.
                                    >
                                    > http://www.sonicscentral.com/kevin7.html

                                    Historically, FG% and Defensive rebounds have been the best indicators
                                    in this kind of study (see chp 6). This kind of study is, well,
                                    flawed. Defensive rebounds are purely a reflection of fg%. So are
                                    total rebounds, to a lesser degree. There are lots of correlations
                                    between stats and this kind of study, while interesting, doesn't tell
                                    you how to use the info to make teams better (my goal). Kevin points
                                    out that turnovers aren't a huge predictor, which is true in the other
                                    large studies I've looked at. That doesn't mean that you can tell
                                    your team to just go out and commit turnovers. Turnovers matter an
                                    immense amount -- but this kind of study doesn't reflect it.

                                    DeanO
                                    www.basketballonpaper.com
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