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Re: Assist tracking update

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  • Dean Oliver
    Plenty of papers available through... http://www.csub.edu/~dberri/ Some abstracts and papers at http://www.csub.edu/%7Edberri/Research.html ...
    Message 1 of 18 , Feb 3, 2004
      Plenty of papers available through...

      http://www.csub.edu/~dberri/

      Some abstracts and papers at

      http://www.csub.edu/%7Edberri/Research.html

      --- In APBR_analysis@yahoogroups.com, bchaikin@a... wrote:
      > > Try this:
      > >
      > > Shot Attempts Points PSA
      > > AST 412 448 1.09
      > > UN 555 523 0.94
      > >
      > > Value of assist (by my calculations) 0.15
      >
      > Still preliminary, but that's pretty close to the difference between
      > points per possession and points per play, i.e., the value of an
      > offensive rebound.
      >
      > I have been continuing my conversations with David Berri, the sports
      > econ professor from Bakersfield. Using an approach that evaluates
      > whether wins come from numerous different stats, he keeps seeing that
      > assists have almost no value. That approach is different than this
      > one and I've been trying to make a point that probably can be
      > clarified just by stats like these (which, as I mentioned before, I
      > didn't see in the smaller study I did in the early '90's). I believe
      > the above is statistically significant. I'll have to follow up
      > sometime to find out what games you were doing, though. You don't
      > want it to be just a couple teams.
      >
      > anyone know if dave berri has any basketball related
      thoughts/musings posted
      > somewhere on the internet, or in print?...
    • schtevie2003
      ... defeating ... of ... is ... Perhaps I should also have added the calculation for New Jersey, the second best passing team in the league, as measured by
      Message 2 of 18 , Feb 3, 2004
        --- In APBR_analysis@yahoogroups.com, "schtevie2003" <schtevie@h...> wrote:
        > In the "how big is big" category, here is how I would contextualize the calculated
        > value. Consider the case of Sacramento, the best passing team in the NBA,
        defeating
        > its opponents by 7.4 ppg (also perhaps league leading). If we take an assist value
        of
        > 0.15 and note that they accumulate about 5.5 more assists than the median team in
        > the league (which by observation appears close to the average) then a fair estimate
        is
        > that their exceptional passing ability explains only about one tenth of their
        > exceptional superiority (calculation: 5.5*0.15/7.4). Does this seem high or low? I
        > guess that my prior would have been that it would have been a slightly higher.
        >
        > ***********
        >
        Perhaps I should also have added the calculation for New Jersey, the second best
        passing team in the league, as measured by assists. For the Nets, assists explain
        about 20% of their victory margin (=3.3*0.15/2.4).

        The interest in this particular stat is this tentative interpretation: for a rather ordinary
        (this year) above-average team, passing, at best (Kidd is the best, no?) can account for
        "at most" 20% of success.

        *************

        > --- In APBR_analysis@yahoogroups.com, "Dean Oliver" <deano@r...> wrote:
        > > --- In APBR_analysis@yahoogroups.com, "nick_scholtz" <nick@l...> wrote:
        > > > Try this:
        > > >
        > > > Shot Attempts Points PSA
        > > > AST 412 448 1.09
        > > > UN 555 523 0.94
        > > >
        > > > Value of assist (by my calculations) 0.15
        > >
        > > Still preliminary, but that's pretty close to the difference between
        > > points per possession and points per play, i.e., the value of an
        > > offensive rebound.
        > >
        > > I have been continuing my conversations with David Berri, the sports
        > > econ professor from Bakersfield. Using an approach that evaluates
        > > whether wins come from numerous different stats, he keeps seeing that
        > > assists have almost no value. That approach is different than this
        > > one and I've been trying to make a point that probably can be
        > > clarified just by stats like these (which, as I mentioned before, I
        > > didn't see in the smaller study I did in the early '90's). I believe
        > > the above is statistically significant. I'll have to follow up
        > > sometime to find out what games you were doing, though. You don't
        > > want it to be just a couple teams.
        > >
        > > DeanO
        > > www.basketballonpaper.com
        > >
        > > >
        > > >
        > > > --- In APBR_analysis@yahoogroups.com, "nick_scholtz" <nick@l...>
        > > > wrote:
        > > > > I think the differences in 3pt and FT% obdcure the basic question:
        > > > >
        > > > > What is the scoring efficiency on plays with "potential" assists and
        > > > > on plays with no assists?
        > > > >
        > > > > For example, look at the data suplied:
        > > > > > 2m-2a 2% 3m-3a 3% ftm-fta ft%
        > > > > > Ast'd 143-263 54% 41-125 33% 39-54 72%
        > > > > > UnAst'd 200-462 43% 12-43 28% 87-113 77%
        > > > >
        > > > > This generated the following.
        > > > >
        > > > > Shot attempts Points Scored PSA
        > > > > Ast 287 366 1.28
        > > > > Un 512 499 0.98
        > > > >
        > > > > Difference in PSA = value of assist = .3
        > > > >
        > > > > This is a far lower value than what I would have expected (I
        > > > > hypothesized a value of 1, John Hollinger uses a value
        > > > > of .67 for the calculations in the Pro Basketball Prospectus)
        > > > >
        > > > > In addition to my suprise at how low the value is, I am suprised by
        > > > > how few FT's come out of potential assist situations. Perhaps it
        > > > makes
        > > > > sense that many fouls come on drives to the basket (not an assist)
        > > > but
        > > > > that is a large reason why the calculated value is so low.
        > > > >
        > > > > Nick Scholtz
      • nick_scholtz
        So I get to be the first person to correct it :) Talking about calculating the value of assists I offered the ... This was computed from the following data ...
        Message 3 of 18 , Feb 5, 2004
          So I get to be the first person to correct it :)

          Talking about calculating the value of assists I offered the
          following calculation:

          > Shot Attempts Points PSA
          > AST 412 448 1.09
          > UN 555 523 0.94
          >
          > Value of assist (by my calculations) 0.15

          This was computed from the following data

          > > 2m-2a 2% 3m-3a 3% ftm-fta ft%
          > > Ast'd 143-263 54% 41-125 33% 39-54 72%
          > > UnAst'd 200-462 43% 12-43 28% 87-113 77%

          The calculation was correct in saying that comparing the assisted
          shot attempts non Unassisted the increase in PSA was 0.15 (which
          seemed low). This is correct as far as it goes, but I forgot the
          final step of distributing the value of the extra points to the
          assists. In this case the 412 shot attempts with potential assists
          generated 61 more points than if the same shots hadn't had potential
          assists. They also were responsible for 184 assists (143 on 2 pt
          basktes, 41 on 3 point shots).

          This leads to a value of an assists of 61/184 or just under 1/3
          point. This is still much lower than I expected but, at least,
          should be the correct calculation.

          I would be very interested if anyone else has collected similar data
          for other teams to see how consistant that number is.

          Nick
        • igor eduardo küpfer
          After 26 games, here s what it looks like: 2m 2a 2% 3m - 3a 3% ftm - fta ft% AST 311 - 570 55% 97 - 252 38% 97 - 142 68% UNAST
          Message 4 of 18 , Feb 12, 2004
            After 26 games, here's what it looks like:

            2m 2a 2% 3m - 3a 3% ftm - fta ft%
            AST 311 - 570 55% 97 - 252 38% 97 - 142 68%
            UNAST 441 - 1037 43% 20 - 95 21% 239 - 318 75%

            DIFF 12% 17% -7%
            p <.001 <.01 ns

            Over the last dozen games I've started tracking shot attempts in the paint
            separate from those outside the paint.

            In2m - In2a In2% Out2m - Out2a Out2%
            AST 89 - 137 65% 69 - 153 45%
            UNAST 129 - 275 47% 66 - 192 34%

            DIFF 18% 11%
            p <.05 ns

            We should be able to combine this with the data from the 82games site which
            shows shot attempt distance for each player in order to begin to credit
            assists properly -- more credit for inside attempts should go to the
            assister. By the end of this season, I'll have enough games scored from a
            wide variety of teams to know how much of the credit should go to the
            passer.

            ed
          • Kevin Pelton
            I ve scored about five Sonics games now ... I need to translate them to HTML. Hopefully the weekend. Are you doing road games as well as home games?
            Message 5 of 18 , Feb 13, 2004
              I've scored about five Sonics games now ... I need to translate them
              to HTML. Hopefully the weekend.

              Are you doing road games as well as home games?
            • Mike G
              ... Trying to figure out what to make of these numbers. I ve reduced this chart to one that represents an average game in the sample: .category. 3pt. 2 pt.
              Message 6 of 18 , Feb 13, 2004
                --- In APBR_analysis@yahoogroups.com, igor eduardo küpfer
                <edkupfer@r...> wrote:
                > After 26 games, here's what it looks like:
                >
                > 2m 2a 2% 3m - 3a 3% ftm - fta ft%
                > AST 311 - 570 55% 97 - 252 38% 97 - 142 68%
                > UNAST 441 - 1037 43% 20 - 95 21% 239 - 318 75%
                >
                > DIFF 12% 17% -7%
                > p <.001 <.01 ns

                Trying to figure out what to make of these numbers.

                I've reduced this chart to one that represents an "average" game in
                the sample:

                .category. 3pt. 2 pt. FT

                "assisted" 4-10 12-22 4-6
                unassisted 1-5_ 17-40 9-12

                Counting 2 FTA as one 'play':

                On 35 "assisted" plays, 40 pts are scored, or 1.143 pts per play

                On 51 unassisted plays, 46 pts are scored, at .902 ppp

                The difference is .216 ppp

                But: In reality, only 16 assists are counted. So, from 16 actual,
                counted assists, 40 pts are produced.

                Therefore, each assist produces 2.5 points; and the difference is
                now 1.585 as the value of each assist.

                (The actual difference, from Ed's 2184 plays, is 1.561)


                We probably all know that a counted assist is only the 'tip of the
                iceberg' which represents all 'good passes' a player executes.
                While there have been players (Kevin Porter? Ray Williams?) who have
                ONLY passed when an assist was to be had, many players get few
                assists, yet are credible passers.

                So the assist represents an "estimate" of the number of
                good, "assist-worthy" passes a player throws.
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