How can park factors change?

[DamnYankees]

Can anyone answer this one big question I've always had about all the "+" stats? It seems to me that if you're playing in the exact same part in consecutive years, the park factor should be identical, no? Unless we really believe weather patterns and winds can have THAT big of an impact, shouldn't park factors pretty much always be static, unless teams change stadia or renovate which changes dimensions?

Why do PFs change?

[andymac]

Well, park factors are relative to the rest of the league. So, any changes to any parks within the league will effect the factor of every other specific park.

[Bay Area Bob]

Another thing is that park factors are always displayed out to a higher degree of confidence than we really have given the sample size.

[mlyons]

Another issue is that the overall park factor is really made up of a number of different components, all of which will affect different teams differently. My favorite example of this is Dodgers Stadium. It generally plays pretty heavily as a pitcher's park. The thing is, though, it's also a really easy park to hit homeruns in. A Dodgers team that's reliant on homerun hitters will see their offense suppressed by the park far less than a team that relies on gap hitters, so the park can play exactly the same, but still affect run scoring differently.

That and they're using a new humidor on the baseballs in Coors Field this season.

[disposableheros]

they change because they arent really park factors.

once you get past using the wrong name for what it measures, it makes more sense.

[andymac]

Originally Posted by disposableheros

they change because they arent really park factors.

once you get past using the wrong name for what it measures, it makes more sense.

I'm not sure I understand this point. Can you elaborate?

[disposableheros]

Originally Posted by andymac

I'm not sure I understand this point. Can you elaborate?

"park factors" dont really measure the effect of the park on the statistical output.


two classic examples:

1) Wrigley field between '66 and '85 - not a single thing that James outlines as effecting park factors changed (dimensions, visibility, foul territory, surface, or climate). yes, climate changed year-to-year, but over the period, its unchanged from average and it cant explain the wildly varying PF. it was a hitter's park every year, but it varied from 104 to 143. if park factors didnt change, why did "park factors"?

2) Sportsman's Park between '20 and '53 - both the Browns and Cardinals played in the same park, but they never had the same "park factor" in any year. exact same physical facility and environmental factors, yet wildly varying PF. some years, its a hitter's park for the Browns, but a pitcher's park for the Cards and there are only a few years in the entire 30+ years that the PF is even close to the same for both teams.

"park factors" are really just the ratio of runs scored by the home and visiting teams in one park vs all other parks, not a measure of how the park itself effects (affects?) statistical output. i think its the name "park factors" that makes people confused about what it is.

[DamnYankees]

Originally Posted by disposableheros

"park factors" dont really measure the effect of the park on the statistical output.


two classic examples:

1) Wrigley field between '66 and '85 - not a single thing that James outlines as effecting park factors changed (dimensions, visibility, foul territory, surface, or climate). yes, climate changed year-to-year, but over the period, its unchanged from average and it cant explain the wildly varying PF. it was a hitter's park every year, but it varied from 104 to 143. if park factors didnt change, why did "park factors"?

2) Sportsman's Park between '20 and '53 - both the Browns and Cardinals played in the same park, but they never had the same "park factor" in any year. exact same physical facility and environmental factors, yet wildly varying PF. some years, its a hitter's park for the Browns, but a pitcher's park for the Cards and there are only a few years in the entire 30+ years that the PF is even close to the same for both teams.

"park factors" are really just the ratio of runs scored by the home and visiting teams in one park vs all other parks, not a measure of how the park itself effects (affects?) statistical output. i think its the name "park factors" that makes people confused about what it is.

Then what is it measuring? If it's just normalizing for the sake of normalizing, that's pointless. The whole idea of Park Factors is that the location you play in affects the output - if the locations don't change, neither should the affects.

[andymac]

A park factor is how the park effects statistics compared to the rest of the league's parks. If other parks change, then the park factor for your park is going to change because their is going to be a new "average". That is essentially what park factors are...they are telling you how a specific park effects each statistic compared to the average park in the league. All of the parks for a certain statistic should average out to be 1.000 if you want the numbers to be giving you something usefull. Otherwise, what do you expect the park factors to be telling you?

[andymac]

"park factors" are really just the ratio of runs scored by the home and visiting teams in one park vs all other parks, not a measure of how the park itself effects (affects?) statistical output. i think its the name "park factors" that makes people confused about what it is.

Yea, I guess some people just don't understand what park factor means. I don't think there is anything wrong with the term.

[andymac]

Originally Posted by DamnYankees

The whole idea of Park Factors is that the location you play in affects the output - if the locations don't change, neither should the affects.

Yes, they should. What do you think a park factor of 1.02 means? It means that the park allows 2% more of whatever you are talking about than the average ballpark. When other ballparks change, the definition of the average ballpark has to change along with it. If a bunch of small ballparks are built that allow a ton of runs to be scored, your ballpark that allowed 2% above the average isn't going to be allowing 2% above the average anymore because the average is going to go up. So, now your ballpark may be below average when it comes to allowing runs. The factor can't stay the same if things around it are changing.

[His Own Bad Self]

Originally Posted by andymac

Yea, I guess some people just don't understand what park factor means. I don't think there is anything wrong with the term.

Couldn't one differentiate between "park factor" and "park run factor"?

[disposableheros]

Originally Posted by andymac

A park factor is how the park effects statistics compared to the rest of the league's parks. If other parks change, then the park factor for your park is going to change because their is going to be a new "average". That is essentially what park factors are...they are telling you how a specific park effects each statistic compared to the average park in the league. All of the parks for a certain statistic should average out to be 1.000 if you want the numbers to be giving you something usefull. Otherwise, what do you expect the park factors to be telling you?

so, what if no stadium in the league changes in any way? will the same exact park factor come up every year?

[andymac]

Originally Posted by disposableheros

so, what if no stadium in the league changes in any way? will the same exact park factor come up every year?

It would likely be close...there are other factors such as weather, simple random chance and stuff like that which would likely make things off slightly. As well as a sample size issue.

[Skipaway]

Originally Posted by disposableheros

so, what if no stadium in the league changes in any way? will the same exact park factor come up every year?

1. It's actually impossible for stadiums not to change from year to year, considering weather is also a strong factor.

2. The way samples are used to calculate park factor is still not providing enough confidence level. Basically the sample size is just not enough to make park factor calculations accurate enough, and the error range is still quite high. That's why a lot of people are trying to miligate that by using weighted five year or three year average.

[andymac]

Originally Posted by jdawgsenior

Couldn't one differentiate between "park factor" and "park run factor"?

Well, what is it you plan on basing your factor that is going to always stay the same on? How are you going to determine where that park is rated? What is the process?

[Skipaway]

Park factor is a generic term anyway. When people try to use more complicated stats to describe a park, we still generally call those stats park factors.

[disposableheros]

even if you did have the exact same physical and environmental conditions in all stadiums for 20 years in a row, PF would change every year due to the only thing not changing, the players in the particular parks.

[disposableheros]

Originally Posted by Skipaway

Park factor is a generic term anyway. When people try to use more complicated stats to describe a park, we still generally call those stats park factors.

and thats all my point is. "park factor" is what is misleading.

[Skipaway]

Originally Posted by disposableheros

the players in the particular parks.

That's supposedly averaged out, and not a factor in park factors. If the player factors are still showing up in park factor calculations, it just means the formula isn't really good.