This debate seems to be about a comparison of the forecasting performance of different metrics. Why make all these vague assertions like “slightly less consistent” and “significantly more consistent”? Why not use an accepted forecasting measure like root mean square error to evaluate these metrics? Oh, I see – you’re an undergraduate. Of course that would be too much work.

All that said, one thing I do find interesting is the heat involved in this debate between some very smart people who agree on the conclusion — that NBA teams overvalue “glory stats” and undervalue other important factors that affect a team’s ability to win games.

I’m also mildly curious as to what you hope to accomplish in posting, Jordan. I hope very much that you’re not a psych major, Jordan. It’s curious psychology to ask someone to do something like modify his model while simultaneously claiming that it’s flawed and that the author of the model is a jerk. It sounds like you have something personal dispute beyond this forum with David.

And “Jason”, lets get one last thing clear, if there was such thing as a “jerk store”, David J. Berri would be their all time best seller.

My understanding of WP is that it’s a measure that looks at the contributions over an extended period and tries to isolate the contributions from that individual, minimizing as much as possible factors of other players and situations. As a predictive model, it relies on WP being relatively constant over time and not changing significantly due to the presence of other players and that the factors measured covary with victories to high degree. I’m not weighing in on whether or not it can do this, but that’s my understanding of what it’s useful for. As a predictive model, it can be used to influence decisions about what players to acquire at what price and what sort of playing time particular players warrant to maximize returns *over a reasonably large sample.* It doesn’t try to maximize particular combinations on the floor in the short time.

If WP works, then the wins for the upcomming season should be predictable if you know what players have done in the past, what players are on a team and what sort of PT particular players are to get. If it works, it should predict changes in the number of wins a team experiences over a significant sample due when a particular player plays for the team or is lost to the team. If it works in this regard, it works and it addressed the question at hand. This doesn’t seem like it’s what you’re particularly interested in, which is fine, but you should realize what a model is addressing and realize that not everyone wants to address the same questions as you. It does not claim to be a model that should be used to manage floor combinations and perhaps the particular combinations are a product of some of the error in the model and perhaps why Dave suggests that coaching does have an impact on wins. That’s entirely plausible, but that’s more refinement or a different model entirely.

One of the beautiful thing about academic endeavours is that a published model can serve as the basis for other models to build upon. This is one of the reasons that I believe it is important to publish if one actually wants to make progress in a field. You are free to take his model and use it if you are inclined and see if you can modify it or aspects of it to answer your own questions. Insisting that *he* cares about the particular question you have (and it seems to go beyond suggestion when you repeat it in thread after thread like a parrot subjected to the tape loop of “adjusted plus-minus”) and that he is somehow obligated to make his model suitable to answer the questions *you* want to address though is rather ridiculous. To insist that your question is the only important one strikes me as rather narrow, though that does appear to be your position.

You are free to see flaws in the model that may be improved by reallocating the individual statistical components via some other method (e.g. weighting them according to +/- or weighing them according to an opportunity cost to other players) and you are free to use the modifications accordingly and to see whether or not this makes the model better either for its initial task or perhaps makes it more applicable to a wider range of questions. You are free to be interested in different questions that should be evaluated by a completely different model, but you should realize when you’re comparing apples to butane lighters and realize that they aren’t the same thing. You do not have any particular right to insist that Dave does the work for you because it’s the question you care about and he is under no obligation to see that your question is the appropriate one and modify his model because you insist it’s a better question.

I am skeptical that any model is able to address *all* questions and I never expect a model to come out initially that is perfect. It’s part of a process to add to what we know, not to arrive immediately at some known end of all knowledge. I don’t know if you’re aware of this or not, but you behave as if you expect everything to answer your questions, as if the measure of a model is how it lives up to answering your questions and have little or no appreciation for not just different approaches, but different questions. You have commented on peer review as if you are skeptical that the system has value and seem to imply that there’s some sort of dishonesty in the whole process, so perhaps this explains why you show little patience with differing opinions. (Are you perhaps a disgruntled academic?)

David has every right to try to address the questions he sees fit to address and you have ever right to care or not, but being a jerk about it says more about you than about his method or model. He is being responsible in trying to publish his views in an arena where others can comment and where others can use what he’s come up with. By saying that he is “refusing” to do somthing and “does not want to take a closer look at his systems’s predictive ability in a more precise way” you seem to suggest that you know his actual thoughts and that he’s being purposefully and willfully negligent and irresponsible. That’s rather rude and shortsighted of the processes that go into actual research, else you’re just adding it for bullying insulting effect and don’t know how to behave in public. I do not know why you chose to behave accordingly, but that’s entirely your issue, not Dave’s. I see no reason why he should pay you any notice at all if you’re so readily willing to question his integrity in your critiques.

I am still confused why a model whose objective is to describe player ability and performance as accurately as possible would not be able to predict how a team does with a given player on the court adjusted for all other factors. This would seem to be the exact definition of player performance.

By refusing to use plus-minus to seperate the effects of players from each other you run the risk of misattributing credit of a team between the individuals within the team. Mr. Berri has clearly made a commitment to his system and does not want to take a closer look at his system’s predictive ability in a more precise way.

With respect to Silverbird’s comments… all of the values we propose for the statistics were derived from regression analysis. I do not know how to state it any more clearly than that. The position adjustments do not impact the predictive power of the model. And I have already commented on the team adjustments.