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December 1, 2010

mgl: Does (one-year) UZR tell us exactly what happened?

Filed under: Chicago White Sox — The Wizard @ December 1, 2010 12:14 pm
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We’ve discussed this before, and the answer is, “No.” Apparently almost everyone keeps forgetting this or doesn’t know it yet.  It differs from all offensive stats in that regard.  There are two kinds of regressions that one needs to do with UZR in order to make any practical sense of it:

1) Regress to estimate what actually happened from what UZR “thinks” happened.  The UZR “engine” does not do any internal regressions.

2) Regress to estimate a player’s true talent from what actually happened. …

October 20, 2010

3 year UZR: Carlos Quentin shouldn’t be playing in the field

Filed under: Chicago White Sox — The Wizard @ October 20, 2010 12:10 pm
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Gross @ THT:

Using these thresholds, here are three-year data (to help smooth out small sample fielding volatility) of all fielders who have played a minimum of 1,500 innings at a given position, put to the “should you be a DH” test via their three-year UZR/150 ratings. (Because Fangraphs’ WAR system doesn’t use UZR data to determine the value of catchers, they are omitted here.) The results are presented below. Click to enlarge. You can download my DH data sheet by clicking here. …

July 6, 2010

mgl: don’t use UZR/150 before 150

Filed under: Chicago White Sox — The Wizard @ July 6, 2010 11:59 am
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the book:

I see it all the time in articles by analysts, such as on Fangraphs.  UZR/150 means nothing if you don’t regress the actual UZR.  If you must quote UZR per 150, at least wait until the player has at least 150 games or so. Otherwise just tell us his UZR and how many defensive games he played.

colin pointed this out in his excellent UZR primer.

April 2, 2010

colin’s excellent UZR primer

Filed under: Chicago White Sox — The Wizard @ April 2, 2010 12:24 pm
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I know I was asked to do a WAR primer next, but I want to take on the major components before I look at position player WAR.  I think going slow will make it easier to make sense of everything when we throw it all in together.  Not to mention some guy named Dave Cameron took basically the same approach at fangraphs.  Whatever that is.

Where to start with fielding?  While errors or fielding percentage get some play, I think defense is assessed by the typical fan with the ever popular Eyeball Test.  This makes sense.  But let’s first figure out…

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