Comments on: Updated In-season 2010 (and 2009) Park Factors This and that about baseball stats. Tue, 16 Jul 2013 17:01:55 +0000 hourly 1 By: tangotiger Thu, 16 Sep 2010 06:54:22 +0000 I agree you need regression. Any time you are dealing with sample data, which, presumably is 100% of the time, and you are trying to find the "rrue" of something, you need to regress.

Sean, if you want, send me a file of your PF like this, and I'll tell you how many games I would add:

Also, what Sean does is not really PF is it? It includes opponents? So, that is a problem too if you apply it over multiple years.

What you REALLY need to do is have a factor that applies only to the park, and then a factor that applies to opponents of that year. And when you do multi-year, you do multi-year on that park-portion, and single-year on the opponent portion.

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By: Johnny Twisto Wed, 15 Sep 2010 20:45:23 +0000 Kelly, your argument is hardly new enough to be worth posting in two threads.

Read Josh's response in the other thread.

There is no "right" or "wrong." What are you trying to measure? If you are measuring value, it only matters what a run is worth in a particular park. That's what B-R's park factors are trying to tell you.

By: Kelly Wed, 15 Sep 2010 19:56:02 +0000 This is sabermetric malpractice! How can you apply one PF to all players on a team, regardless of whether they are RH or LH, power hitters or singles hitters, speedy or slow? To show the folly of this I need go no further than Coors Field:

Home OPS - Road OPS (Career)
- Seth Smith, +.321
- Carlos Gonzales, +.289 (Rox years only)
- Clint Barmes, +.178
- Todd Helton, +.145
- Troy Tulowitski, +.121
- Colorado Rockies Team, +.220 (2010 only)

So, Coors helps everyone, but it helps some players a hell of a lot more than others. Other parks like Fenway with their idiosyncratic measurements show even more pronounced differences.

Folks here have vested interests in OPS+, WAR, etc., so I'm sure I'll get flamed, but anyone who stops to think about this for even a minute will know that I am right.

By: Charles Saeger Wed, 15 Sep 2010 19:52:24 +0000 Sean: have a hundred game or so regression to 1.00 in these. That will kill off some of the annoying motion. I made a note on Tom Tango's blog, and he's more of an expert than I in this, so he might have something to say as well.

By: David Wed, 15 Sep 2010 19:31:32 +0000 If you were to run it daily, it would be important to account for new stadiums, right? For example, Target field shouldn't have 2009 numbers reflecting. I know you know that. I'm just trying to help!

By: Sean Forman Wed, 15 Sep 2010 19:18:13 +0000 I was already thinking that I would update it daily next year, perhaps something like

PF 2011 = (PF 2010 + (1-X)*PF 2009 + X* PF 2011)/2

where X = percentage of the season completed thus far.

By: Thomas Wed, 15 Sep 2010 19:11:43 +0000 Is there any way this can get updated monthly or maybe quarterly next season?

By: Sean Forman Wed, 15 Sep 2010 17:39:41 +0000 Kingcrab, you will need to look at runs scored and allowed at home and road and the innings played in each to answer that question.

By: kingcrab Wed, 15 Sep 2010 16:57:09 +0000 how does cbp and att park have the same number? cbp, as mentioned earlier, has the rep of being a bandbox and att has the rep of being a big time pitcher's park.