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Re: st: cendif


From   alfonsa leiva <arfons74@yahoo.com>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: cendif
Date   Fri, 23 Nov 2012 04:51:39 -0800 (PST)

Thanks again 

--- On Thu, 11/22/12, Roger B. Newson <r.newson@imperial.ac.uk> wrote:

> From: Roger B. Newson <r.newson@imperial.ac.uk>
> Subject: Re: st: cendif
> To: statalist@hsphsun2.harvard.edu
> Date: Thursday, November 22, 2012, 4:53 PM
> If you want to compare 2 intervention
> groups separately with the control 
> using -somersd- and -cendif-, then you need to use an -if-
> qualifier for 
> each intervention-control pair. If your grouping variable is
> -grupo-, 
> with values 0 for control, 1 for Intervention 1, and 2 for
> Intervention 
> 2, then you can compare interventions 1 and 2 with the
> control by typing:
> 
> xi i.grupo, noomit
> somersd grupo T6convulsion if inlist(grupo,0,1), transf(z)
> tdist 
> cluster(medcod3);
> cendif T6convulsion if inlist(grupo,0,1), by(_Igrupo_0)
> transf(z) tdist 
> cluster(medcod3);
> somersd grupo T6convulsion if inlist(grupo,0,2), transf(z)
> tdist 
> cluster(medcod3);
> cendif T6convulsion if inlist(grupo,0,2), by(_Igrupo_0)
> transf(z) tdist 
> cluster(medcod3);
> 
> This will give the 2 median intervention-control differences
> in outcome, 
> with confidence limits, and also confidence linits, and
> P-values, for 
> the Somers' D parameters of outcome with respect to each
> intervention 
> compared to the control group.
> 
> I hope this helps. Let me know if you have any more
> queries.
> 
> Best wishes
> 
> Roger
> 
> 
> Roger B Newson BSc MSc DPhil
> Lecturer in Medical Statistics
> Respiratory Epidemiology and Public Health Group
> National Heart and Lung Institute
> Imperial College London
> Royal Brompton Campus
> Room 33, Emmanuel Kaye Building
> 1B Manresa Road
> London SW3 6LR
> UNITED KINGDOM
> Tel: +44 (0)20 7352 8121 ext 3381
> Fax: +44 (0)20 7351 8322
> Email: r.newson@imperial.ac.uk
> Web page: http://www.imperial.ac.uk/nhli/r.newson/
> Departmental Web page:
> http://www1.imperial.ac.uk/medicine/about/divisions/nhli/respiration/popgenetics/reph/
> 
> Opinions expressed are those of the author, not of the
> institution.
> 
> On 22/11/2012 13:55, alfonsa leiva wrote:
> > Dear stata user
> >
> > In the between group analisis (control vs
> Intervention1/ control vs Intervention2/Intervention1 vs
> Intervention2)of a three arm cluster trial,
> >
> >   I can get p- values by somersd:
> >
> > xi, noomit: somersd   T6convulsion
> i.grupo, taua transf(z) tdist cluster(medcod3)
> >
> > testparm _I*
> >
> >
> > . testparm _I*
> >
> >   ( 1)  _Igrupo_1 = 0
> >   ( 2)  _Igrupo_2 = 0
> >         Constraint 2
> dropped
> >
> >         F(  1, 
>   46) =    7.02
> >              Prob
> > F =    0.0110
> >
> >
> >
> > Could i use also Hodges-lehman estimates by cendiff to
> report differences between groups?
> >
> >
> > xi,noomit: cendif   T6irritabilidad ,
> transf(z) tdist cluster(medcod3) by(grupo)
> >
> >
> >   Percent    Pctl_Dif 
>    Minimum     Maximum
> >          50   
>        0       
>    0       
>    0
> >
> >
> > I apreciatte any comment
> >
> >
> >
> > Thanks
> > *
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