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Re: Value of Assists

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  • 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 1 of 19 , Jan 5, 2004
      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 2 of 19 , Jan 5, 2004
        (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 3 of 19 , Jan 8, 2004
          --- 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 4 of 19 , Jan 8, 2004
            --- 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 5 of 19 , Jan 8, 2004
              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 6 of 19 , Jan 8, 2004
                --- 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 7 of 19 , Jan 9, 2004
                  --- 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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