I posted this to the SAS List several days ago and
received responses from persons who wanted to do the
same or indicated they understood the reasons we wanted
to do what we did, but none that actually answered my question.
Sorry to those of you for whom this represents a cross posting.
The original post:
A colleague and I have longitudinal radiographic data on
children prior to and following hip treatment. The
progression of various structures observed by x0ray were
used to assess various aspects of the hip recovery.
The protocol asked that the radiographs be obtained at fixed
intervals (e.g., pre-trt and 6, 12, 18, 24, 36 and 48 months
post-trt.). As is almost always the case, some of these time
points were missed completely and others were followed up at
intervals other than specified.
We used proc EXPAND to simultaneously "center" obtained data
points to the protocol based times and to estimate (impute?)
values for the missing cases x-rays.
Examination of the results were encouraging. When we randomly
removed some points, the estimated values were generally quite
close.
Now for my question:
Do any of you know of any references that have used the EXPAND
procedure to accomplish these purposes? Medical references
or methodological studies demonstrating the value of this approach
would be preferable, but references in any field would be acceptable.
________________________________________________________________
_____________
Kevin F. Spratt | |
Iowa Testing Programs (ITP) ( )
University of Iowa Back Care (UIBC) \ \_ University
Iowa Spine Research Center (ISRC) \ * \ of Iowa
224-D Lindquist Center \ / Hawkeyes
The University of Iowa |____________ )
Iowa City, Iowa 52242 V
(319) 335-5572 (voice)
(319) 335-6399 (fax)
[EMAIL PROTECTED] (e-mail)
________________________________________________________________
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