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st: RE: Comparison of a distribution with a value from the literature


From   Laurel.Copeland@med.va.gov
To   statalist@hsphsun2.harvard.edu
Subject   st: RE: Comparison of a distribution with a value from the literature
Date   Fri, 18 Apr 2003 12:50:38 -0500

You can use the immediate form of ttest, ttesti. See -help immed-

-----Original Message-----
From: Andrea Baccarelli [mailto:andreastata5@hotmail.com]
Sent: Friday, April 18, 2003 1:43 PM
To: statalist@hsphsun2.harvard.edu
Subject: st: Comparison of a distribution with a value from the
literature


I have the following question:

I am studying how the continuous variable A varies after a specific 
treatment.
In addition to compare A after the treatment with A before the treatment or 
in controls (no treatment), I need to compare it also with standard 
reference values from the literature.
Let's say that most book assume that A is equal to 1.0 with SD=0.2.

I thought to use the ttest command:

ttest A=1.0

I have two points:
1-This not take into account the variability (SD=0.2) of the measure taken 
from the literature. Does anyone have any suggestion about how to include it

in the analysis?
2-Most variables in the study are not normally distributed. Is there any 
non-parametric test I can use to this end? [Stata's "ranksum" do not allow 
comparisons to a fixed value]

Thanks,
Andrea









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