Pitchers don't really need to be taken into accoun...

2009-05-12T15:38:00.000-07:00

Pitchers don't really need to be taken into account to measure the actual park factor, because looking at what a team does in it's home and road games is essentially the same sample of pitchers over a long enough length of time. For the Rangers, for example, the home sample is the Rangers' pitchers pitching to the rest of the league's hitters, and the rest of the league's pitchers against the Rangers' hitters. The road sample is the exact same thing. So if you just want to measure the effect of the park itself, you don't have to worry about it. There are small variations in who pitches or hits where how often, but not enough to worry about. The overall effect, if you're looking at enough games in calculating the park factor, is minuscule compared to the amount of work it would take to account for. It's the same for defense, or any other quality of a team's players. As far as the park factor itself goes, it shouldn't make a difference, because it's equally present in both the home and road sample.

The reason you account for hitters and pitchers is to account for the quality of opposition a player faces and has nothing to do with the park itself. In looking at the quality of pitching a team has and adjusting for it, you are really looking at what the team gave up. For example, for a run PF, how many runs the team allowed compared to average. Or for an ISO PF, the ISO the team allowed compared to average. And park-adjusted, of course, since we've already figured the park factor at this point. When we look at what the team allowed to the opposing offense, we call it "pitching", but really, it's a combination of pitching and defense. For example, if the Rangers allowed 1.24 times the ISO an average team would have allowed in the Ballpark in Arlington, that is the combination of the total extra bases their pitching and defense allowed relative to the number of at bats the opposition had. It's mostly pitching and simpler to just say pitching, but it's a combination of both. Just like ERA or WPA for pitchers is actually a combination of pitching and defense-which is why we have stats like FIP. So defense is already accounted for in what we call "pitching".

Left-/right-handed splits can be calculated in more or less the same way. You would just look at only the stats by left-handed or right-handed hitters instead of entire team stats. I don't know of anyone that publishes these, so you'd have to do them yourself. In some cases, it would probably make a significant difference (like Fenway, for example), but what we have is at least better than nothing, and for most parks the difference is probably not that much. The biggest problem with this is that you can start to run into team composition problems: if a team has a lot of lefties, then the home sample will be skewed high because more of your hitters will be hitting at home in the park you are measuring for, which is a problem because players hit better at home. So your PF will tell you that lefties hit better there even if they don't. Or you have the opposite problem for teams with relatively few lefties. That doesn't mean you can't calculate it, but you would have to account for how many left- or right-handed PAs each team had and add that adjustment into the formula. So, you could do it, it would just be more complicated.

my main concern with park factors is that they don...

2009-05-11T21:25:00.000-07:00

my main concern with park factors is that they don't take enough information into account. it seems like they're simply a measure of what happened in a given park, not why it happened. opposing pitchers are taken into account, as you mentioned, but is there any compensation for opposing defenses? also, is there any way to distinguish the effects that parks have on right/left-handed hitters? or are all these various other factors rendered moot because they don't have much of an outcome on park factors when it's all said and done?

Comments on 3-D Baseball: A Note About Park Factors

Pitchers don't really need to be taken into accoun...

my main concern with park factors is that they don...