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Re: Assist tracking update
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 In APBR_analysis@yahoogroups.com, "Michael Tamada" <tamada@o...>
wrote:
>
Indeed  what jumped out at me from Ed's original post
> But before we say that the assists aren't helping the 3point shooters,
> we need to look at the "opportunity cost": the assist might still have
> value because it gave the 3point shooter the chance to put up the shot
> in the first place.
was the *huge* percentage of 3FGA that were assisted.
If I'm reading his numbers correctly only 36% of all
2FGA were assisted, while **74%** of all 3FGA were
assisted. That sounds to me like not only are assists
helping the 3 point shooters  the assist is *THE* major
factor in getting off a good 3. 0 Attachment
Original Message
From: Charlie Board [mailto:cboard@...]
Sent: Monday, February 02, 2004 8:40 AM
 In APBR_analysis@yahoogroups.com, "Michael Tamada" <tamada@o...>
wrote:
>> But before we say that the assists aren't helping the 3point shooters,
A good point, but now we're getting into things which are really
>> we need to look at the "opportunity cost": the assist might still have
>> value because it gave the 3point shooter the chance to put up the shot
>> in the first place.
>
>Indeed  what jumped out at me from Ed's original post
>was the *huge* percentage of 3FGA that were assisted.
>If I'm reading his numbers correctly only 36% of all
>2FGA were assisted, while **74%** of all 3FGA were
>assisted. That sounds to me like not only are assists
>helping the 3 point shooters  the assist is *THE* major
>factor in getting off a good 3.
hard to measure. The major factor probably was indeed the pass
to the (presumably open) 3point shooter. But to accurately put
a value on that, we need to know what would've happened in the
absence of that nice pass, a very hard hypothetical situation to
measure.
It's somewhat analogous to the assisted/unassisted basket situation,
except taken a step further: the question now isn't the impact of
the pass on the shooter's FG%, the question is whether the shooter
got a look at the basket and a potential shot in at all.
While we can measure FG% on assisted and unassisted baskets, we
don't have stats on what sort of shot would've been attempted in
the absence of the nice pass to the 3point shooter.
I supposed we could use unassisted 2pt FG% as a rough guesstimate
(with cripple layins subtracted first).
MKT
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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:> 2m2a 2% 3m3a 3% ftmfta ft%
This generated the following.
> Ast'd 143263 54% 41125 33% 3954 72%
> UnAst'd 200462 43% 1243 28% 87113 77%
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
 In APBR_analysis@yahoogroups.com, "Michael Tamada" <tamada@o...>
wrote:> Original Message
shooters,
> From: Charlie Board [mailto:cboard@t...]
> Sent: Monday, February 02, 2004 8:40 AM
>
>
>  In APBR_analysis@yahoogroups.com, "Michael Tamada" <tamada@o...>
> wrote:
>
> >> But before we say that the assists aren't helping the 3point
> >> we need to look at the "opportunity cost": the assist might
still have
> >> value because it gave the 3point shooter the chance to put up
the shot
> >> in the first place.
> >
> >Indeed  what jumped out at me from Ed's original post
> >was the *huge* percentage of 3FGA that were assisted.
> >If I'm reading his numbers correctly only 36% of all
> >2FGA were assisted, while **74%** of all 3FGA were
> >assisted. That sounds to me like not only are assists
> >helping the 3 point shooters  the assist is *THE* major
> >factor in getting off a good 3.
>
> A good point, but now we're getting into things which are really
> hard to measure. The major factor probably was indeed the pass
> to the (presumably open) 3point shooter. But to accurately put
> a value on that, we need to know what would've happened in the
> absence of that nice pass, a very hard hypothetical situation to
> measure.
>
> It's somewhat analogous to the assisted/unassisted basket situation,
> except taken a step further: the question now isn't the impact of
> the pass on the shooter's FG%, the question is whether the shooter
> got a look at the basket and a potential shot in at all.
>
> While we can measure FG% on assisted and unassisted baskets, we
> don't have stats on what sort of shot would've been attempted in
> the absence of the nice pass to the 3point shooter.
>
> I supposed we could use unassisted 2pt FG% as a rough guesstimate
> (with cripple layins subtracted first).
>
>
> MKT
>
> 0 Attachment
uh . . . make that "obscures"
I don't mean to suggest that other questions are uninteresting (I
would, for example, suggest that the reason why FT% is lower in
assisted situations is because more of the FT's are being shot by big
men and fewer by guards  who have a higher FT%). I would also note
that the observed 5% difference in assisted and unassisted 3 pointers
would work out to a 7.5% difference in "true shooting %" which is
closer to the 2 point percentage difference. It's still true that the
true shooting % for assisted 3 point shots is lower than that for
assisted 2 point shots which may or may not mean that teams should
stop shooting 3 point attempts :)
Also I think the table below is incorrect  I didn't realize that 3
pointers had already been separated out.
Try this:
Shot Attempts Points PSA
AST 412 448 1.09
UN 555 523 0.94
Value of assist (by my calculations) 0.15
Nick Scholtz
 In APBR_analysis@yahoogroups.com, "nick_scholtz" <nick@l...>
wrote:> I think the differences in 3pt and FT% obdcure the basic question:
makes
>
> What is the scoring efficiency on plays with "potential" assists and
> on plays with no assists?
>
> For example, look at the data suplied:
> > 2m2a 2% 3m3a 3% ftmfta ft%
> > Ast'd 143263 54% 41125 33% 3954 72%
> > UnAst'd 200462 43% 1243 28% 87113 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
> 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 0 Attachment
 In APBR_analysis@yahoogroups.com, "nick_scholtz" <nick@l...> wrote:> Try this:
Still preliminary, but that's pretty close to the difference between
>
> Shot Attempts Points PSA
> AST 412 448 1.09
> UN 555 523 0.94
>
> Value of assist (by my calculations) 0.15
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:
> > > 2m2a 2% 3m3a 3% ftmfta ft%
> > > Ast'd 143263 54% 41125 33% 3954 72%
> > > UnAst'd 200462 43% 1243 28% 87113 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 0 Attachment
> Try this:>
Still preliminary, but that's pretty close to the difference between
> Shot Attempts Points PSA
> AST 412 448 1.09
> UN 555 523 0.94
>
> Value of assist (by my calculations) 0.15
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?...
 0 Attachment
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.
***********
 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:
> > > > 2m2a 2% 3m3a 3% ftmfta ft%
> > > > Ast'd 143263 54% 41125 33% 3954 72%
> > > > UnAst'd 200462 43% 1243 28% 87113 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 0 Attachment
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?... 0 Attachment
 In APBR_analysis@yahoogroups.com, "schtevie2003" <schtevie@h...> wrote:> In the "how big is big" category, here is how I would contextualize the calculated
defeating
> value. Consider the case of Sacramento, the best passing team in the NBA,
> 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
is
> the league (which by observation appears close to the average) then a fair estimate
> that their exceptional passing ability explains only about one tenth of their
Perhaps I should also have added the calculation for New Jersey, the second best
> 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.
>
> ***********
>
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) aboveaverage 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:
> > > > > 2m2a 2% 3m3a 3% ftmfta ft%
> > > > > Ast'd 143263 54% 41125 33% 3954 72%
> > > > > UnAst'd 200462 43% 1243 28% 87113 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 0 Attachment
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
This was computed from the following data
> AST 412 448 1.09
> UN 555 523 0.94
>
> Value of assist (by my calculations) 0.15
> > 2m2a 2% 3m3a 3% ftmfta ft%
The calculation was correct in saying that comparing the assisted
> > Ast'd 143263 54% 41125 33% 3954 72%
> > UnAst'd 200462 43% 1243 28% 87113 77%
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 0 Attachment
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 0 Attachment
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? 0 Attachment
 In APBR_analysis@yahoogroups.com, igor eduardo küpfer
<edkupfer@r...> wrote:> After 26 games, here's what it looks like:
Trying to figure out what to make of these numbers.
>
> 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
I've reduced this chart to one that represents an "average" game in
the sample:
.category. 3pt. 2 pt. FT
"assisted" 410 1222 46
unassisted 15_ 1740 912
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, "assistworthy" passes a player throws.
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