Re: st: is there a -regress- command equivalent to the pair matched ttest?

[David Airey <david.airey@Vanderbilt.Edu>]

For the use of xtmixed for classical experimental designs, see this  
page:

http://www.ats.ucla.edu/stat/stata/faq/xtmixed.htm

-Dave

On Dec 9, 2008, at 9:12 AM, Sam Norton wrote:

> Jose Maria
>
> You can, if you really want to, use -xtmixed-.  Phil Enders
> presentation at the West Coast Stata Users Group meeting in 2007 gives
> an example of how to use -xtmixed- to estimate a RM-ANOVA.  Since
> ANOVA is based on deviations from the grand mean -xi3- (available from
> SSC) is needed to create effect coded variables.
> http://www.stata.com/meeting/wcsug07/repeated_anova.pdf
>
>
> --
> Sam Norton
> samjnorton@gmail.com
> Research Student
> Centre for Lifespan & Chronic Illness Research
> University of Hertfordshire
>
> 2008/12/9 David Airey <david.airey@vanderbilt.edu>
> > A paired ttest is equivalent to a repeated measures ANOVA with two  
> > levels to the repeated factor. You can see the regression  
> > equivalent below.
> >
> > webuse fuel, clear
> > list, clean
> > ttest mpg1 == mpg2
> > local t = r(t)
> > generate subject = _n
> > list, clean
> > reshape long mpg, i(subject) j(repeat)
> > list, clean
> > anova mpg repeat subject
> > anova, regress
> > test repeat
> > local F = r(F)
> > display `F' "=" `t'^2
> > xi: regress mpg i.repeat i.subject
> >
> >
> >
> > On Dec 8, 2008, at 7:05 PM, josemaria wrote:
> >
> > > Dear Statalisters:
> > > I am not sure whether it makes sense or not, but is there a sort  
> > > of -regress- command that allows to conduct a pair-matched - 
> > > ttest-, but with other independent variables?
> > > I tried using -xtmixed-, but the result is not the same.
> > > A contrived data set could be:
> > > matching_identification  outcome ocasion variable_not_matched
> > >                     1            1                1                0
> > >                     1            2                2                0
> > >                     2            3                1                0
> > >                     2            5                2                1
> > >                     3            2                1                0
> > >                     3            4                2                1
> > >                     4            6                1                1
> > >                     4            5                2                1
> > > To perform the pair-matched ttest  it is necessary to -reshape-  
> > > and to use -ttest outcome1==outcome2-, losing the independent  
> > > variable_not_matched.
> > > Thank for any orientation.
> > > Regards,
> > > José Maria
> > >
> > > Jose Maria Pacheco de Souza, Professor Titular (aposentado)
> > > Departamento de Epidemiologia/Faculdade de Saude Publica, USP
> > > Av. Dr. Arnaldo, 715
> > > 01246-904  -  S. Paulo/SP - Brasil
> > > fones (11)3061-7747; (11)3768-8612
> > > fax (11)3714-2403
> > > www.fsp.usp.br/~jmpsouza
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