Park Factor: how reliable?
Thursday, January 24, 2013
Two teams, one park, different park factors.
So how come the park factor is different for one team almost every season? Because baseball is played in non-uniform playing areas a park factor is needed to try to equate stats...
In St. Louis when the teams had the same BPF three consecutive years it was different each year: 106, 107, 104. Same thing in Philadelphia for two consecutive years: 97, 98...
Park factor is used to compute OPS+ and ERA+, two bedrocks of current conventional wisdom. I realize that parks change from one season to the next, even the configuration of the same park changes, and that there are different parks in the two leagues but this indicates how little we know about this important stat ...
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Click link to view data and interactive graphs.
AL:
BPF max: 2011 Rangers Ballpark in Arlington 117
BPF min: 1964 Dodger Stadium (Angels) 90
StDev max: 2011 6.97
StDev min: 1913 2.295
NL:
BPF max: 1995 Coors Field (Rockies) 129
BPF min: 2008 Petco Park (Padres) 88
StDev max: 1995 8.95
StDev min: 1952 1.7
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