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Re: [APBR_analysis] Re: Value of Assists
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 But if you're looking for some completely teammateindependent, contextindependent 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@...
 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 AssistsBut if you're looking for some completely teammateindependent, contextindependent 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 highpercentage 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 inherentmarksmanship 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 preMagicesque 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 requote 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   In APBR_analysis@yahoogroups.com, nick@l... wrote:
> I just joined this group so apologies if the following throughts
are old news.
>
volunteers
> > From: "Kevin Pelton" <kpelton08@h...>
> > The value of assists? To get a legitimate answer would probably
> > require at least a seasonlong or leaguewide study where
> > tracked whether unmade shots would have been credited an assist
or
> > not. Ask DeanO how difficult that would be.
assist
>
> I've been trying to think of a good way to measure the value of an
> 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.
aren't
>
> To get a perfectly accurate number we would need two stats that
> 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
shoot
> player receiving the pass misses the shot.
>
> The latter is of crucial importance. Imagine a jump shooter who can
> 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 2040 (40 pts) and the pg has racked up 13 assists. If
there
> were no pg to pass the ball he would shoot 1440 (28 pts). In this
pt.
> case the marginal value of an assist is clearly (4028)/13 or ~ 1
>
and
> If we were to just look at the first situation (2040, 13 assists)
> say "he went 727 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
pts. To
> generating an assist) and would set the value of an assist at 1.48
> get the true value of an assist we need to understand that not every
the two
> potential assist results in a basket.
>
> Lacking any way to compute those percentages directly (if we had
> 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.
rather
>
> I decided that it made more sense to look at assists as a team stat
> 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.
possessions,
>
> I took all of the team data from 8889  0102 and computed
> assist/possession (app) and points per possession (ppp).
app and
>
> I then did a simple linear regression on the relationship between
> ppp and generated the following values:
posession
>
> PPP = 1.0733* APP + 0.7794
>
> This sets the marginal value of an assist at 1.07 (changing one
> from 0 to 1 asssits increased the predicted team score by 1.07
points).
>
It
> This methodology has a couple problems, some intentional some not.
> 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.
Cleveland
>
> You could, if you wanted, phrase the question as "did moving from
> 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.
>
seems like
> In addition, I agree with John Hollinger that, intuitively, this
> 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.
wants to run
>
> I'm curious to know what everyone makes of that and if someone
> the calculation on a larger dataset.
199495
>
> It would also be interesting to look at the differences between pre
> and post 199495, as the number of 3pointers attempted increased
> dramatically that year.
>
> Comments would be appreciated.
>
> 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 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
Really? I admit I haven't had a chance to read your book yet but this
> mean little. Some good teams have needed assists to be good.
> Others haven't. It is a style thing.
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 (8889 through 0102) 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
8990 Trailblazers, 9697 heat, and 9495 Spurs. In addition the 8889
Pistons and 9900 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 backcourt but very few from anywhere
else.
Nick Scholtz  (A) But if you're looking for some completely teammateindependent, contextindependent 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 highpercentage 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 8990 and 9091 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 preMagicesque 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 requote 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@...
  In APBR_analysis@yahoogroups.com, "nick_scholtz" <nick@l...>
wrote:>
this
> 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
> statement seems very suprising to me. As I've said I think an assist
if
> almost always means that an offense is functioning well. While an
> offense can function without generating assists I would be suprised
> a good offense would consistantly fail to generate assists.
for
>
> I would be perfectly willing to believe that the number of assists
> the team leader in assists doesn't correlate to success but that's
What the book says (as it's better than my memory):
> different.
"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   In APBR_analysis@yahoogroups.com, "Dean Oliver" <deano@r...>
wrote:
> What the book says (as it's better than my memory):
Interesting. I thought that a year or two ago there was a study done
>
> "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...
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 email if
you're going to be in the area.
Nick Scholtz 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  In APBR_analysis@yahoogroups.com, "nick_scholtz" <nick@l...>
wrote:>  In APBR_analysis@yahoogroups.com, "Dean Oliver" <deano@r...>
http://www.sonicscentral.com/kevin7.html
> 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.
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   In APBR_analysis@yahoogroups.com, "Kevin Pelton" <kpelton08@h...>
wrote:>  In APBR_analysis@yahoogroups.com, "nick_scholtz" <nick@l...>
Historically, FG% and Defensive rebounds have been the best indicators
> 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
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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