25 Sep
2002
25 Sep
'02
10:33 a.m.
Yeah, panel attrition is a big issue. Amelia in general is a pretty good
second-best approach for most applications, where the 1st best approach
differs from application to application and is generally a lot harder to
use. The question in this case is how well you can do in this case.
What I'd do is to give it a try but to carefully check how well its
fitting. In principle, there's nothing wrong with doing it, but I'd
compare the imputed to the nonmissing values and see whether they are
roughly similar. e.g., look at a scatterplot of say PID time 1 by PID time
2 with the imputed values in red. the imputed values can be different
than the others because of panel attrition _bias_ that is being corrected
by Amelia through other variables (not in the scatterplot but measured in
the first wave). But if the red dots are far from the others, then I'd go
another step and figure out why. If you can't find a good reason (like
attrition being due to high income), then I'd worry about what Amelia is
doing.
overall of course, the more you impute, the more your answers are
dependent on the model.
Gary
: Gary King, King(a)Harvard.Edu http://GKing.Harvard.Edu :
: Center for Basic Research Direct (617) 495-2027 :
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On Tue, 24 Sep 2002, Randy Stevenson wrote:
Gary,
I was writing to get your opinion on a common data analysis problem.
Ray Duch and I are reanalyzing a large number of election studies for
our book on comparative economic voting. We are using amelia to deal
with missing data, but are debating what to do for cases in which a
respondent in the pre-election survey did not respond in the
post-election survey. Since we are using quite a few variables from
most of the post election surveys, we are asking a lot from amelia to
fill in so many missing values (even though for many there is reasonable
information in the first stage to help impute them). Most of the
codebooks include an anlysis of non-responde and whther there seem to be
anything systematic about who these people are and most conclude that
there is little systematic in the non-responses. I assume that you have
thought about this particular kind of missing data and wondered if you
had any thoughts.
Randy
___________________________________________
Randy T. Stevenson
Albert Thomas Associate Professor of Political Science
Dept. of Political Science /MS 24
Rice University
6100 Main St.
Houston, Texas 77005
phone: 713 348-2104
fax: 713 348-5273
email: stevenso(a)ruf.rice.edu
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