laika wrote:Doctor MJ wrote:
I don't know what to tell you man. If the team did worse without Kobe, he'd do better by this stat. It's pretty simple. You don't have to value the stat or agree with conclusions people reach from the stat, but it's no great mystery what the cause is.
You can agree that his rating is extremely irregular and most likely wrong. He would necessarily do better by this stat only if adjusted +/- was 100% reliable and valid- which it clearly is not. I don't know why you keep talking about the team doing worse without Kobe- as I've shown in multiple ways the Lakers play significantly worse without him.
Short of a mathematical proof showing that adjusted +/- produces invalid results due to statistical errors I don't know what else I could show you. What we know-
-Adjusted +/- is known to have problems when dealing with collinearity and substitution effects. The Lakers have a large collinearity problem since 2 starters spend almost all their time playing with Bryant.
-Adj +/- can be very unreliable, with big swings for no apparent reason.
-Bryant historically has had a very good adj +/-.
-There has been remarkable continuity on the Lakers from last year to this year. The players are the same, the team performance is the same, and Kobe's stats are very similar.
-Every other statistical indicator shows Kobe is having a good year. His net +/- is good, his Per is good, his net production is good and virtually every Laker lineup plays significantly worse when Kobe is off the court. From what I can see there is nothing else that supports his adj +/- number.
-Kobe is the largest outlier among all of the top players.
Man, I keep getting hung up in conversations to night where we talk about abstract intellectual stuff, and people are getting confused with basic language. I don't mean that as an insult to you in any way, such things can happen to anyone, but it's frustrating.
When I say "Kobe's APM would be better if his teammates did worse without him", I mean "Kobe's APM would be better if his teammates did EVEN worse THAN THEY ACTUALLY DO without him".
Is it damning for the stat's math that he rates poorly given that the team does better with Kobe on the floor than when he's off the floor? Not at all. Kobe's hardly alone that this happens to. The answer is always the same: Given the players Kobe gets to play with disproportionately relative to the combinations of players who play for the Lakers with Kobe not on the floor, the gap in performance is less than expected.
It's up to each person to decide what that means to them, and clearly I don't do anything like a straight mapping of it, but the description of what's happened is clear.
The issues of reliability you speak of are real, and if you consider them so severe that the stat should be completely ignored at all times, that's up to you. I don't throw stats out like that though. The lack of reliability just means I view the numbers with a great deal of fuzziness, and draw conclusions with great caution. Kobe's stats are WAY out there to the point they are impossible for me to ignore...and the result is that I have him a few slots lower in my MVP rankings than other people. This is really not that bold folks.
Re: "Kobe's been good by this stat before, and he and the team are so similar to previous years."
Kobe's playing 5 minutes per game less this year than last year and the team's SRS is much better than last year's team. If you are not seeing a shift in the play of his supporting cast, you aren't paying close enough attention.
laika wrote:Here's a hypothetical, just for fun- If adj +/- were wrong, how would you know? Unless you were a true statistical expert, then you would not. As far as I know no one has come close to proving that adj +/- is valid and reliable in every situation. If anything, people have shown situations where it would give flawed results. Of course common sense would dictate that you discard the adj +/- number when it disagrees with every other piece of evidence, as it does here.
I think it's time to let go of the lamppost in this particular case and admit that Kobe's adj +/- number is really flawed this year.
If I were a true statistical expert? Whoa. I'd say you're thinking about this all wrong. This isn't something where if we only had a good enough statistician in the room, he could tell us which is right, and which is wrong. There is uncertainty here, which is the point where the consulting statistician comes back to the client and together they use his intuition about stats and their intuition about the context of the data to come to the most reasonable conclusions.
Am I a good enough statistician to play those two roles? Well you're free to decide whatever you want. I've got a sufficiently large ego than I'm not terribly concerned. Should you believe me? I don't know what to tell you. You want a resume?
Honestly for me what this all comes down to is that I'm having fun - I'm concerned about being wrong primarily as a means for self-improvement. I don't want others to believe something simply because I believe, and you'd better believe that there is no authority that I'll defer to without cause.
Re: flawed this year. You know I don't know if I'd disagree with that statement. If the stat was perfect, I could use it as a direct proxy for how good of a year Kobe has had. I cannot, so in some sense it is flawed. Flaws don't mean you discard though, they mean you evaluate how much stock you can give the thing in question. As I've said before, out of the 450 players in the league, I have Kobe about 3 or 4 slots lower than than some other people. This is really not that big of a thing.
