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| 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 * * For searches and help try: * http://www.stata.com/help.cgi?search * http://www.stata.com/support/statalist/faq * http://www.ats.ucla.edu/stat/stata/