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Re: st: sampsi


From   Phil Schumm <pschumm@uchicago.edu>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: sampsi
Date   Fri, 19 Aug 2011 16:47:52 -0500

On Aug 19, 2011, at 2:09 PM, Eurich, Dean wrote:
> Sorry for the confusion. We are not really interested in the longitudinal changes over the longer term (I.e., 5 years). What we want to do do is basically - Does very short term changes in brain function at time of diagnosis (I.e., 8 weeks) predict 5 yr mortality.  So in a sense the 8 week change score a "baseline value". We are not interested if the patients continue to decline or not.


Understood.  Given this, I'm not really sure where the controls come in, but I don't need to know.  I just wanted to be clear that the power calculation we were discussing was for comparing the mean 8-week change among cases (i.e., those with ALS) to that among a corresponding set of controls.


-- Phil


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