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Re: park factors

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  • KJOK
    I posted my Park Factor Calculation worksheet to the FILES section, which has both 1 year and 3 year BPF and PPF calculations thru 2003. Note that the team
    Message 1 of 4 , Mar 8, 2006
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      I posted my Park Factor Calculation worksheet to the FILES section,
      which has both 1 year and 3 year BPF and PPF calculations thru 2003.

      Note that the team ID's are TB VII ID's, not BDB/Lahman Team ID's.

      THANKS,
      Kevin

      --- In baseball-databank@yahoogroups.com, "John Walsh"
      <walshj58@...> wrote:
      >
      > Hi Kevin,
      >
      > Thanks for your reply. I don't think, though, that the change from
      3-yr park
      > factor to 1-yr park factor occured in the 2001 season. I think the
      agreement
      > in 2000 was fortuitous. Here's a table with the standard deviation
      of the
      > difference of the 1-yr and 3-yr park factors.
      >
      > +--------+------------+
      > | yearid | SD 1yr-3yr |
      > +--------+------------+
      > | 1990 | 6.2354 |
      > | 1991 | 11.2559 |
      > | 1992 | 8.2969 |
      > | 1993 | 6.1793 |
      > | 1994 | 13.3250 |
      > | 1995 | 7.9646 |
      > | 1996 | 6.8963 |
      > | 1997 | 6.4826 |
      > | 1998 | 6.3557 |
      > | 1999 | 1.9439 |
      > | 2000 | 1.6479 |
      > | 2001 | 1.8454 |
      > | 2002 | 1.5691 |
      > | 2003 | 1.3780 |
      > | 2004 | 3.0494 |
      > +--------+------------+
      >
      > It looks like the change occurred in 1999.
      >
      > -John Walsh
      >
      > On 3/7/06, KJOK <kjokbaseball@...> wrote:
      > >
      > > John:
      > >
      > > I believe that in the past the Lahman/BDB Park Factors came from
      the TOTAL
      > > BASEBALL 3 year park calculation. As I did the park factor
      calculation
      > > re-checks in the last TOTAL BASEBALL edition, I can tell you
      that, for the
      > > Angels, the calculations were:
      > >
      > > YrID LgID TmID park bpf ppf
      > > 2000 AL ANA Edison International Field 102.72910 103.18840
      > > 2001 AL ANA Edison International Field 102.44840 101.94480
      > > 2002 AL ANA Edison International Field 99.83886 99.33416
      > >
      > > So yes, it appears that beginning in 2001 the Lahman database
      has 1 year
      > > factors instead of the 3 year ones.
      > >
      > > THANKS,
      > > Kevin Johnson
      > >
      > > *John Walsh <walshj58@...>* wrote:
      > >
      > > Hi,
      > >
      > > I've been doing some research on park effects and I'm seeing
      something
      > > strange in the Lahman DB park factors. I understand that the
      park factors
      > > from the Teams table are 3-yr park factors, calculated as
      described on the
      > > bb-ref.com site:
      > >
      > > http://www.baseball-reference.com/about/parkadjust.shtml
      > >
      > > The documentation for the Lahman DB also says that the park
      factors are
      > > 3-year numbers.
      > >
      > > The thing is, they look more like 1-yr park factors to me. The
      following
      > > table illustrates the problem:
      > >
      > > +------+------+--------+--------+--------------------------------
      +-------------+
      > >
      > > | team | year | r_home | r_away | round(100*r.r_home/r.r_away,0)
      |
      > > bpf+ppf-100 |
      > >
      > > +------+------+--------+--------+--------------------------------
      +-------------+
      > > | ANA | 2000 | 880 | 853 | 103
      |
      > > 103 |
      > > | ANA | 2001 | 759 | 662 | 115
      |
      > > 113 |
      > > | ANA | 2002 | 722 | 773 | 93
      > > | 94 |
      > >
      > > +------+------+--------+--------+--------------------------------
      +-------------+
      > >
      > > I think the columns are self-explanatory. Well, the 3rd column
      is just the
      > > ratio of runs scored at home to runs scored away for Angels
      games. It's the
      > > simplest 1-yr park effect you could imagine. (Note, the factor
      of 2 that
      > > accounts for only half of the games being played at home is not
      included
      > > here.) The last column gives the result from the Lahman
      database, which,
      > > according the the URL given above, does quite a complicated
      calculation of
      > > park factor. I'm basically averaging the batter and pitching
      park factors
      > > and removing the factor of two so you can compare with the 1-yr
      factors.
      > >
      > > As you can see the Lahman DB park factors (which are the same as
      those
      > > shown at bb-ref.com) are very similar to the 1-yr factors. In
      fact, if we
      > > calculate a simple 3-yr factor for 2001, using the ratio of runs
      at home to
      > > runs away for the period 2000-2002, we'd get 103, much different
      from the
      > > Lahman DB number of 113.
      > >
      > > Have I don't something wrong here or are the Lahman DB (and bb-
      ref) park
      > > factors actually 1-yr factors, even though they are advertised
      as 3-yr
      > > factors?
      > >
      > > thanks,
      > >
      > > -John Walsh
      > >
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