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st: RE: "Repeated-measures" form of linear regression?


From   "Cohen, Elan" <cohened@upmc.edu>
To   "'statalist@hsphsun2.harvard.edu'" <statalist@hsphsun2.harvard.edu>
Subject   st: RE: "Repeated-measures" form of linear regression?
Date   Fri, 17 Sep 2010 16:59:04 -0400

Pietro,

See -xtreg-.  In your case, something like:

xtreg D F, i(subject)


- Elan
 

> -----Original Message-----
> From: owner-statalist@hsphsun2.harvard.edu 
> [mailto:owner-statalist@hsphsun2.harvard.edu] On Behalf Of 
> Pietro Mazzoni
> Sent: Friday, September 17, 2010 16:41
> To: statalist@hsphsun2.harvard.edu
> Subject: st: "Repeated-measures" form of linear regression?
> 
> Dear Statalist,
> 
> My question is not specific to Stata, but I am hoping that 
> someone can at least point me to the topic of statistical 
> testing on which I can do more reading to answer this 
> question. I appreciate any suggestions.
> 
> My hypothesis, in a motor control experiment, is that there 
> is a linear relationship between a perturbation (say, force 
> F) and a response (say, lateral deviation D). I obtained data 
> from several subjects who were tested at various levels of 
> force and whose response was a particular deviation for each 
> force pulse. I feel that it would be incorrect to perform a 
> linear regression of D vs. F on the pooled data, because this 
> would ignore within-subject correlations. I see this data as 
> analogous to repeated-measures ANOVA, because multiple pairs 
> of (F, D) were collected within each subject.  So my 
> intuition tells me I should perform linear regression within 
> each subject, and then somehow combine these results across 
> the group, but I don't know what procedure might be the 
> analog of rm-ANOVA for regression. One suggestion I got was 
> to perform individual regressions within each subject and 
> then average the values of the slopes and intercepts obtained 
> to estimate slope and intercept f!
>  or the group. But I am more interested in establishing 
> whether there is a significant relationship at the group 
> level (R square, p value for the group) than in determining 
> the parameters of the regression, and I don't know how to 
> combine the R squares or p values obtained for individual subjects.
> 
> Where can I read about repeated-measures approaches for 
> continuous variables/regression?
> 
> Thanks in advance for any ideas.
> 
> Pietro
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