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Rockets Adjusted +/-

Discussion in 'Houston Rockets: Game Action & Roster Moves' started by durvasa, Feb 7, 2008.

  1. durvasa

    durvasa Member

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    basketballvalue.com has been a useful site this season for looking up how well different combinations of players play together, not to mention how matchups between different combinations of players on opposing teams went. They just added adjusted +/- stats for every player. Here are the current numbers for the Rocket players:

    http://basketballvalue.com/teamplayers.php?year=2007-2008&team=HOU

    Some comments and limitations about the methodology used can be found here:
    http://82games.com/barzilai2.htm

    According to this analysis, Rafer Alston is probably our most valuable player (*half of clutchfans faint*). I used the word "probably" because there is a large standard error with this approach; some may even argue that the errors are so large that it isn't useful at all. What it represents is a best guess based on how the score changes with the players on the court.

    Perhaps more surprising is how poorly Yao Ming scores by this analysis. Yao was one of the best players according to adjusted +/- a year ago, but now it tells us he is one of the least effective players in the league. While boxscore stats tend to be relatively stable from one year to the next, one might expect that how well a player is actually playing is actually more volatile because effectiveness is so context-dependent. Should we conclude from this rating that Yao has not adjusted well at all to Adelman's system, and in fact we have generally been a better team without him on the court?

    You may not lend any credence to these numbers, and that's fine. I'm highly skeptical myself, because watching the games I know all the positive things Yao brings the team. I think he's one of the best players in the game, so this result is sort of mystifying. Half a season is a pretty small sample for this type of thing, so I'll chalk it up to that. I do wonder, however, whether the Rockets are using adjusted +/- stats as part of their evaluation process of players, and if so whether they are concerned about this.
     
    #1 durvasa, Feb 7, 2008
    Last edited: Feb 7, 2008
  2. zforrest

    zforrest Member

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    This was the case last year, too, when our starting five lead the NBA in levono stats. We also had a leading trio in McGrady-Alston-Battier. I think most people attribute this to the fact that Alston enters and exits the game with the more meaningful players, which impacts Alston's individual +/-
     
  3. durvasa

    durvasa Member

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    Actually, the starting lineup has performed much worse this season compared to last (which one might expect, with the coaching change), but Rafer has had a strong adjusted +/- in both years (again, also expected, considering how much each coach has depended on him). I want to stress the very small sample size, so perhaps we can just call it a fluke. I believe Rosenbaum in his original study used 3 or 4 seasons worth of information to evaluate players using adjusted +/-. He even mixed in some box-score stats (he called it "statistical adjusted +/-") to reduce the noise. The more stats-savvy people on here maybe have a better idea how useful/useless all this is.

    I do think people seriously underrate Alston's value to this team, in general. One need only consider the two games we played without him in Toronto and Philadelpha. Those were major crash and burn games. It is a mystery to me how a player with seemingly no great NBA skills can have such an impact. I guess that's a pretty good demonstration of how important the point guard position is, when even a mediocre PG like Rafer can be so integral.
     
    #3 durvasa, Feb 7, 2008
    Last edited: Feb 7, 2008
  4. AroundTheWorld

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    +/- numbers are overrated.

    Edit: I just saw Alston's and Yao's rating on that site.

    I have to retract my statement.

    They are not overrated, they are idiotic and misleading.
     
  5. zforrest

    zforrest Member

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    I said nothing of this year's starting lineup.

    As said already, +/- is overrated, even misleading. Don't think too much of it.
     
  6. Carl Herrera

    Carl Herrera Member

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    Look at the standard error... it's rather large. Like you said, it's a small smaple size and I know Morey would take he sample size and the resulting standard error into account when he looked at the numbers.

    If there is any issue, I think Yao's numbers have to do with adjustment to the system. When used correctly, he is a force... but when you fail to protect him on D, and don't get him involved on offense properly (for example, by force-feeding him when you shouldn't have), you hurt yourself.

    Van Gundy found a formula that worked well enough last season... Adelman's first half season has been an experience in trying different methods, some of them have worked, some not so well.
     
  7. airmanz

    airmanz Member

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    These stats are meaningless....

    Their standard errors are all more than 2.

     
  8. choujie

    choujie Member

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    Even though +/- depends on too many factors, Yao is not being used effectively on offense end like last year is a fact.
     
  9. durvasa

    durvasa Member

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    Pretty much how I looked at it. I think, if nothing else, it reflects that Yao has had a tough time adjusting to the system, and Adelman has had a tough time adjusting the system to Yao. That's been my impression from all the interviews given over the course of the season, and this sort of underlines that. It also might partially explain how the team could have struggled so much in terms of winning games between the two years, despite an apparent upgrade in talent. Hopefully the Rockets have turned a corner, though.

    I do think it's kind of ironic that the two players that frustrate fans the most with their lack of offense happen to rate the highest based on a measure that's essentially orthogonal to boxscore stats. It's funny how that works out.
     
  10. Carl Herrera

    Carl Herrera Member

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    Agreed about the turning the corner.... there are signs that indicate that they may have. We'll see. It's been a strange first half of a season.

    Although the numbers don't tell us that it is BECAUSE player X is on/off the floor that we strubble, it does tell us that we Do struggle when player X is on/off the floor. It is interesting to see how well Rafer stacks up... it seems for whatever reason (coincidence or otherwise), the team hasn't played well without overall without him.
     
  11. DaDakota

    DaDakota Balance wins
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    Screw stats, all that matters is Wins and losses, the rest is just wasting time.

    I think Yao needs 16 rebounds tonight to get his average back to 11 a game.

    :D

    DD
     
  12. landryfans

    landryfans Member

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    check few other teams 's worst player

    Jazz: D Williams
    Portland: Roy
    Sun: Amare

    ...

    sth. is wrong with stats,
     
  13. landryfans

    landryfans Member

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    even Paul, Chris is negative in this stats ,
     
  14. durvasa

    durvasa Member

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    I don't know, to me this is sort of like saying "screw biomedicine, all that matters is life and death, the rest is just wasting time." Perhaps that's what a doctor would have thought 500 years ago! A lot of these stats may not tell us as much as we'd like, but I think the general principle of using objective methods to better understand the game and guide decision making is a sound one.
     
  15. JeopardE

    JeopardE Member

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    Usually when you see a statement like this, it indicates that the poster has just suffered an episode of cognitive dissonance. I've said it before: people dismiss stats when they seem to contradict their own (usually otherwise baseless) opinions.

    Anyways ... durvasa, I've been seeing this trend with Yao all season long. There definitely is a drastic difference from last year -- this time around for some reason, there just hasn't been any significant dropoff in team performance when he isn't on the floor versus when he is. The numbers are probably skewed by the early season situation when the whole team was struggling. One thing I wish bbvalue.com would do is provide data on splits, like over the past month, road/away, that sort of thing. Would definitely give a lot more insight. One thing has been constant though -- this team plays like crap without Rafer Alston, both offensively and defensively.
     
  16. badgerfan

    badgerfan Member

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    Yeah, but your numbers have to actually be meaningful. The standard errors on those +/- statistics is huge, meaning essentially that you can have no confidence in them.

    In other words, saying the moon is 300,000 km away from the earth plus or minus 100,000 km is technically correct. But it's useless if you're trying to plot trajectories for a moon landing.

    Also, medicine and a lot of the other sciences often saw progress when treatments were prescribed on the basis of efficacy alone. In other words, we don't know why it works but it seems to, so let's keep doing it.
     
  17. badgerfan

    badgerfan Member

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    Small sample size leads to high standard error, which makes me wonder if they're useful/meaningful.
     
  18. lalala902102001

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    Whenver Rafer's name is put in the same sentence as the "most valuable player", you know something is wrong.

    Those +/- numbers are generally meaningless IMO. It depends heavily on who you play with on the court. The starters typically have better +/- numbers than the bench players because they pay with the better unit out there.
     
  19. AroundTheWorld

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    LOL, on the Timberwolves, almost everyone has a positive +/-, only Al Jefferson has -23.01. How dumb is that...
     
  20. JeopardE

    JeopardE Member

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    Frankly I've never been impressed by the adjusted +/- stat ever since I first saw it on 82games.com ... something has to be wrong with the methodology when the non-adjusted statistics generally make more sense than the adjusted ones. It probably has to do with the fact that the adjusted stat is even more heavily influenced by the production of a player's backup than the non-adjusted one.

    That said ... Al Jefferson is a horrible defender for a big man. Even worse than Amare (as bad as Amare is, at least he blocks shots). I'm not surprised at all that he's rated so low. That's why he puts up great stats and the Wolves keep losing.
     

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