Comments on: Layups: Nate Silver on Carmelo Anthony & the Usage-Efficiency Debate

By: huevonkiller

huevonkiller — Fri, 21 Jan 2011 12:38:47 +0000

Thank Crow, those are some interesting conclusions.

As for Shaq and Z? Yeah they're getting killed on 82games.com last season, it isn't only because the Cavs are undersized.

By: Crow

Crow — Fri, 21 Jan 2011 08:08:10 +0000

If a new metric were to try to supplement or replace existing ones it would be good to see the predictive performance comparisons.

Perhaps the shot defense component should be a weighted multi-season estimate instead of just the current season. That too may raise flags with some, but if it gets you closer to modeling reality in a more stable / helpful way I'd be for it.

By: Crow

Crow — Fri, 21 Jan 2011 08:01:10 +0000

It is still an estimate but perhaps the fairest one? Blending one on one shot defense with help defense impact whereas Defensive Rating and counterpart PER each only have one. If you don't want to use this Adjusted +/- Factor then I'd think it would make more to sense come up with some blend of statistical data on team level opponent shot defense and counterpart defense than to continue with just one value. While the original authors may not want to update their metrics "officially" and in their own use, and they can have that view, it has become more common to see adjusted metrics such as adjusted PER (for other reasons) and adjusted WP48 (for rebounds) so some interested parties and users could also do an adjusted Defensive Rating, if they have the desire and time to put it together. Or if an adjusted old metric is an undesirable mash-up then a new metric may be the way to go. I am encouraged by EvanZ's EZPM.

By: Crow

Crow — Fri, 21 Jan 2011 07:39:41 +0000

huevonkiller is being critical of the lack of individual ratings for shot defense in Defensive Rating and perhaps also that it is team average for all minutes and not for when they are actually on the court. I recognize these shortcomings as well though I don't blame them on Neil. It was a simplification that was better than no consideration of shot defense- at least for guys on different teams.

Simple PER though had and has no shot defense component at all. Counterpart PER has such estimates. That however assumes all shot defense is counterpart shot defense and the data is inferred based on assumed match-ups and not from videotape so it also has issues and imperfection.

Evan's EZPM has team shot defense divided among players actually on the court but at this point it is still even to all. Some weight to counterpart data might be an improvement. Evan and I batted the idea of differential credit shares for team shot defense perhaps based on shot distance at his site. Jeff Fogel and I also discussed whether the credit / blame of shot defense could be better modeled with variable credit by position instead of equal shares at hoopdata.

Some improvements in linear metrics are possible on this issue / may happen / may gain support. Or perhaps the shot defense factor estimate of Adjusted +/- could be calculated and plugged into where either the boxscore metric hole for it is or the crude current estimate is.

By: Jason J

Jason J — Thu, 20 Jan 2011 18:42:28 +0000

Huev - I think another significant reason for the defensive collapse in Cleveland (aside from Bron and Delonte, their two top perimeter defenders, jetting to Miami and Boston) is the coaching change. Brown was a Pop disciple and a very good defensive coach. Not that Scott isn't a good defensive coach, but he's got a different philosophy and doesn't have the pieces to make it work. They also lost Moon who was a decent defender for them. And Z and Shaq, so they're undersized. You're right. They don't have the same defensive personnel at all.

By: Guy

Guy — Thu, 20 Jan 2011 17:03:19 +0000

Ed/30: I think you are right that Silver's analysis was quick-and-dirty, and far from convincing. However, Pelton's study (linked in Neil's post) was much better and deeper, and still found a strong "Melo effect." Because Pelton looks at players with and w/o Melo, he is controlling for the most important factors Silver didn't control for (coach, team, age, and -- to some extent -- teammates). Berri's study cannot yet be considered as evidence on the other side, because he declined to report his regression coefficient and standard error. He said only that Melo's coefficient was not statistically significant. It's entirely possible that his regression found a positive Melo effect similar in size to Pelton's (or even Silver's), and yet it was still not statistically significant given Berri's small sample. And despite multiple requests at this blog that he provide his regression results, he hasn't responded. So unless/until he does, his reported result should have no standing (or, if you're cynically inclined, you might take his failure to disclose results as evidence in favor of Pelton's/Silver's findings). And the truth is that Berri's seasonal w/ or w/o Mele data is methodologically far inferior to Pelton's on/off court data in any case.

By: AYC

AYC — Thu, 20 Jan 2011 16:59:32 +0000

Not even Hollinger thinks PER does a good job of measuring defense....

By: EvanZ

EvanZ — Thu, 20 Jan 2011 16:56:32 +0000

Thanks, Neil. Good stuff!

By: Neil Paine

Neil Paine — Thu, 20 Jan 2011 14:58:43 +0000

Re: #29 - Dean later went on to expand on the BoP study of skill curves and even a basic (for the public's eyes) version of what he was doing for Denver showed an inverse relationship with a significance level at which there was no way it was due to chance.

http://www.sonicscentral.com/apbrmetrics/viewtopic.php?p=3998#3998

Eli Witus took a much more in-depth look using 5-man unit data and found that units whose members were forced to take on more possessions underperformed their expected efficiency before a skill curve compensation, while units whose members took on fewer possessions outperformed their expectations before a skill curve adjustment:

http://www.countthebasket.com/blog/2008/03/06/diminishing-returns-for-scoring-usage-vs-efficiency/

Also, Dan Rosenbaum, Daniel Myers, and I have each consistently found a "diminishing returns" effect to true shooting attempts per minute when predicting on-court impact from box score stats.

http://www.82games.com/comm30.htm

http://sonicscentral.com/apbrmetrics/viewtopic.php?t=2603

http://www.basketball-reference.com/blog/?page_id=4122

As for Huevon, care to link to any of the "ignorant" analysis I've supposedly done regarding defense?

By: Ed

Ed — Thu, 20 Jan 2011 13:15:06 +0000

Sorry but Nate's anaylsis was VERY sloppy and I'm surprised to see it being featured here. Dberri has posted a lengthy reply which details many of the problems with Nate's anaylsis.

http://dberri.wordpress.com/2011/01/17/commenting-on-nate-silver%E2%80%99s-melo-effect/

In the end, it COULD be that Nate is correct....but there's no way to draw that conclusion from his anaylsis.