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re: st: repeated measures


From   "Airey, David C" <david.airey@vanderbilt.edu>
To   "statalist@hsphsun2.harvard.edu" <statalist@hsphsun2.harvard.edu>
Subject   re: st: repeated measures
Date   Wed, 27 Feb 2013 14:16:51 +0000

.

Sounds like you tried some models and anova complained about the bse term.

I find the description a little hard to follow. What is a multiplex test? What are the outcome/dependent variables and measures? What are the predictors? What was the study design? It sounds complicated. Were the measures "resulta_1" and "resulta_2" replicates at the same time (technical replicates you would be willing to average because they represent trying to get a better measure) or were they collected at different times (you were interested in change over time in those measures)?

If you used -anova- or -xtmixed- you would need to reshape your data to long format.

-manova- and -sem- would allow analysis of repeated measures in wide format.

-Dave

> I have a dataset that includes results from a multiplex test by 2
> collection methods, and a criterion standard result for each
> collection method. In wide form, by subject, it looks like this:
> subject resulta_1 resultb_1 resultc_1 criterion_1 resulta_2 resultb_2
> resultc_2 criterion_2
> 
> In order to assess the effect of each result as predictor of the
> criterion standard, I know that I have to adjust for non-independence
> of the observations, but how do I do that for the outcome?  I would
> use repeated measures ANOVA, but the dependent variable is also
> repeated.  And what would be my bse term??
> 
> A little lost.  Thank you
> 
> --
> Harrison Alter, MD, MS, FACEP



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