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RE: st: Difference of means and t-test


From   "Nick Cox" <n.j.cox@durham.ac.uk>
To   <statalist@hsphsun2.harvard.edu>
Subject   RE: st: Difference of means and t-test
Date   Mon, 14 Jun 2010 17:19:43 +0100

-- except that will surely overstate the strength of the conclusions, in
so far as the real distributions are unlikely to be exactly Gaussian. 

Nick 
n.j.cox@durham.ac.uk 

Richard Williams

At 04:41 PM 6/12/2010, mmolina@uniroma3.it wrote:

>I am working with three different samples.
>When I deal with two of them, I can calculate the difference of means
and
>t-test by doing:
>
>ttesti obs1 mean1 std1 obs2 mean2 std2, unequal
>
>As I have three groups, I am also interested in testing the null: mean1
=
>mean2 = mean3 , under the alternative that at least one mean is
different.
>
>Could you please give me some advice?

Are you using ttesti because you do NOT have the raw data? If you do 
have the raw data, it would be easier to use ttest and then use anova 
or oneway for your three means test.  If you don't have the raw data, 
I don't think there is anything like a onewayi -- one possible 
approach might be to use corr2data to create a fake data set with the 
deisred Ns, means and standard deviations.


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