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Wednesday, February 26, 2014

James: On the Relative Importance of Pitching Categories (Registration Required)

Part I:

Which pitching stats are most closely connected to value?... I took all pitchers in history who pitched 199.0 to 201.0 innings… The more often a category agrees with the bottom line, the more closely it is connected to Value.

What is Value?  I decided to use Fangraphs WAR as “true value”.

Part II:

1)  Home Runs Allowed (55.4%).  Among the twelve pitching categories that I studied, Home Runs Allowed are the poorest predictor of overall value…

2)  ERA (57.4%)...

3)  Runs Allowed Per 9 Innings (58.9%)...

4)  WHIP (60.01%)... 

5)  Strikeout Rate (60.5%)...

6) Won-Lost Records (60.9%)... First of all, we should make sure everyone understands that the “ERA” that performs poorly here is ERA not adjusted for the league ERA…

I started to think about this article in January, when I was on Brian Kenny’s show, and Brian asked me whether I would join in the effort to get rid of the “Win” stat.   I said “No”, and the reason I said “No” is that I’m not generally in favor of getting rid of information…

I might argue that fans in general have a stronger grasp of the biases inherent in won-lost records from the teams on which people pitched than they do of the ERA bias from leagues…

The won-lost record has a tremendous advantage over almost any other stat, in that the winning percentage is always .500 in every decade, in every year, in every month—and in every park…

6)  Walks Per Nine Innings (61.2%)... 

5)  Winning Percentage (61.5%)....

4)  Season Score (62.6%) [this is a new stat that assigns weights to the basic pitching stats - TDA]... 

3)  Relative ERA [63.6%]... This Relative ERA was NOT park-adjusted…

1 and 2)  Strikeouts Minus Walks (65.2%) and Strikeout to Walk Ratio (65.4%) essentially tied as the best predictors of True Value, among the twelve categories studied.

Of course, it is possible that Strikeouts and Walks perform best as a predictor of Wins Above Replacement because Fangraphs is relying too heavily on strikeouts and walks in their calculation of the pitcher’s value… I will have to tell you, honestly, that I was surprised by how many cases there are in which F-WAR gives seemingly irrational answers in comparing two pitchers… I am not saying that Fangraphs is wrong in any of these comparisons; it is quite possible that, if I knew more about the calculations, I would agree with them.  I know very well that many times what seems like an obvious conclusion from the statistics will not stand up to closer scrutiny, and the researcher will wind up arguing that what appears to be true is not actually true.  I’ve seen that myself a thousand times.

But I also know very well, from years of doing it, that the process of weighing and measuring every stat so as to determine overall value is a treacherous and difficult task, and that there are thousands of ways you can get the wrong answer.    I’ve done that myself a great many times, as well.  I am less convinced than I would like to be that these evaluations are accurate.

The District Attorney Posted: February 26, 2014 at 12:50 PM | 11 comment(s) Login to Bookmark
  Tags: bill james, sabermetrics

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   1. Sean Forman Posted: February 26, 2014 at 02:27 PM (#4662918)
Is Bill aware that fWAR for pitchers is basically just a combination of Walks, SO and HR?
   2. PreservedFish Posted: February 26, 2014 at 02:35 PM (#4662929)
It looks like he figured that out halfway through the study...

Of course, it is possible that Strikeouts and Walks perform best as a predictor of Wins Above Replacement because Fangraphs is relying too heavily on strikeouts and walks in their calculation of the pitcher’s value… I will have to tell you, honestly, that I was surprised by how many cases there are in which F-WAR gives seemingly irrational answers in comparing two pitchers…

I am less convinced than I would like to be that these evaluations are accurate.


Nice work Bill!

Do you think the Red Sox get his A-game, or is he just a Statistician Emeritus at this point?
   3. Baldrick Posted: February 26, 2014 at 02:44 PM (#4662941)
So...a statistic that inputs strikeouts, walks, and HR is really sensitive to good numbers of strikeouts and walks?

I'm shocked.
   4. dave h Posted: February 26, 2014 at 03:04 PM (#4662974)
I want fWAR for pitchers to die in a fire.
   5. cardsfanboy Posted: February 26, 2014 at 03:15 PM (#4662996)
I want fWAR for pitchers to die in a fire.


I hate fWar as much as anyone, but it has it's uses. I mean realistically all you really need is fip and could probably ignore fWar, but it's another way at looking at fip. There are other stats that need to die first (any stat that is /9 based of course, needs to be replaced by a percentage)
   6. Zach Posted: February 26, 2014 at 03:32 PM (#4663018)
I was going to say, you could just look up the formula if you care that much.
   7. PreservedFish Posted: February 26, 2014 at 03:58 PM (#4663042)
This is seriously embarrassing.
   8. The District Attorney Posted: February 26, 2014 at 05:07 PM (#4663084)
Even if BB, K, and HR weren't inputs into fWAR, I still don't think I understand what this was attempting to prove. If the pitcher's "value" is minimizing run scoring, by whatever measurement... and we already know how much BB/K/HR/etc. contribute to run scoring, via stats as old as Runs Created... then, well, what are we doing?

It seems like it'd be a lot more useful to examine what stat best predicts how good the guy will be next year. (I'm sure that's been done a million times, but I haven't seen it in quite a while, and I'd be curious to see an update.)
   9. Robert in Manhattan Beach Posted: February 26, 2014 at 05:44 PM (#4663119)
I will have to tell you, honestly, that I was surprised by how many cases there are in which F-WAR gives seemingly irrational answers in comparing two pitchers… I am not saying that Fangraphs is wrong in any of these comparisons

They're wrong. It's bad enough to do a study like this but why on earth would you share it with people?
   10. Rob_Wood Posted: February 27, 2014 at 12:37 AM (#4663308)
I don't blame Bill for this is an example of the law of unintended consequences. The internet allows (encourages) all sorts of "analyses" that would not have seen the light of day in an era of peer review -- and by peer review I mean showing it to someone else before publishing it.
   11. PASTE Thinks This Trout Kid Might Be OK (Zeth) Posted: February 27, 2014 at 11:16 PM (#4663912)
Do you think the Red Sox get his A-game, or is he just a Statistician Emeritus at this point?


Likely a little of both. Even among hobbies the stuff he posts on BJO is only a time-killer and small income-booster for him; his serious hobby is reading and writing about murder stories.

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