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Re: st: Averages for missing values


From   SamL <saml@demog.berkeley.edu>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: Averages for missing values
Date   Thu, 8 Sep 2005 16:01:51 -0700 (PDT)

These methods are frowned upon?  Which method in particular is the object
of the frown?  I guess I am puzzled, because mean substitution comes in a
few flavors.  There is substituting the mean and leaving it at that.  I
assume this is widely understood as problematic.  And then there is
substituting the mean and adding a dummy variable to the model that
indicates whether the mean has been substituted.  Is there any problem
with this second approach?

Thanks a bunch.
Sam

On Thu, 8 Sep 2005, Richard Williams wrote:

> At 03:45 PM 9/8/2005, TinnaLaufey Asgeirsdottir wrote:
> >Hello Statalist.
> >
> >Before I give myself carpal tunnel syndrome I might ask:
> >
> >Is there a command to replace missing values with averages?
> >
> >What I am currently doing is:
> >
> >generate varnameAVE=varname
> >summarize varnameAVE
> >replace varnameAVE=[here I use the mouse to copy from the results
> >window to the command window] if varnameAVE==.
>
> Adding to your list of suggestions: try the -impute- command, e.g.
>
> gen one = 1
> impute varname one, gen(varnameAVE)
>
> For other variations (e.g. subgroup means) see p. 10 and later of
>
> http://www.nd.edu/~rwilliam/stats2/l12.pdf
>
> Let me add that this may be showing you how to do evil, however; most
> of these sorts of methods are now frowned upon.  See Paul Allison's
> Sage book entitled "Missing Data".  You may wish to check out Patrick
> Royston's -ice- package, which is also discussed in Stata Journal, V.
> 5 # 2, pp. 188-201.
>
>
> -------------------------------------------
> Richard Williams, Notre Dame Dept of Sociology
> OFFICE: (574)631-6668, (574)631-6463
> FAX:    (574)288-4373
> HOME:   (574)289-5227
> EMAIL:  Richard.A.Williams.5@ND.Edu
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> WWW (department):    http://www.nd.edu/~soc
>
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