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RE: st: adjusted Mann-Whitney/Wilcoxon test


From   "Newson, Roger B" <r.newson@imperial.ac.uk>
To   "'statalist@hsphsun2.harvard.edu'" <statalist@hsphsun2.harvard.edu>
Subject   RE: st: adjusted Mann-Whitney/Wilcoxon test
Date   Thu, 9 Apr 2009 21:39:54 +0100

As David said, the -somersd- package, downloadable from SSC, can estimate stratified versions of rank parameters. The user has a choice of parameters, which may be Kendall's tau-a, Somers' D, or a Theil-Sen median slope. All of these parameters are available in stratified versions, restricted to comparisons within strata defined by a categorical variable. And the -somersd- package has 3 .pdf manuals, which the user can download with the package, in which the methods and formulas are explained.

I hope this helps.

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.

-----Original Message-----
From: owner-statalist@hsphsun2.harvard.edu [mailto:owner-statalist@hsphsun2.harvard.edu] On Behalf Of David Airey
Sent: 09 April 2009 18:23
To: statalist@hsphsun2.harvard.edu
Subject: Re: st: adjusted Mann-Whitney/Wilcoxon test

To me, stratified generally means controlling for a non-continuous  
covariate.

-Somersd- provides rank-based statistics for group comparisons  
allowing for strata.

-Dave

On Apr 9, 2009, at 10:45 AM, Constantine Daskalakis wrote:

> I have the same question as Ricardo.
>
> By stratified, we mean controlling for another covariate:
>
> Wilcoxon of Y by X, controlling for Z
>
> StatXact does this stratified Wilcoxon.
>
>
> David, the parallel is Mantel-Haenszel for dichotomous outcome.
>
> So, the command would look something like this:
>
> ranksum y x, by(z)
>
> or
>
> ranksum y, by(x) strata(z)
>
>
> On 4/9/2009 10:44 AM, David Airey wrote:
>> .
>> If ttest generalizes to regress, then ranksum generalizes to what?
>> There is a lot of literature on ranksum tests with clustered data  
>> if that's what you mean. Maybe you can define your data more  
>> precisely...
>> On Apr 9, 2009, at 8:44 AM, Ricardo Ovaldia wrote:
>>>
>>> Dear all,
>>>
>>> Is there a way to adjust the -ranksum- test for covariates? Or is  
>>> there another way to do an adjusted Mann-Whitney U test? Something  
>>> similar to relationsip between ttest and regress.
>>>
>>> Thank you,
>>> Ricardo.
>>>
>>> Ricardo Ovaldia, MS
>>> Statistician
>>> Oklahoma City, OK
>
>
>
> -- 
>
>
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>
> Constantine Daskalakis, ScD
> Associate Professor,
> Thomas Jefferson University, Division of Biostatistics
>   1015 Chestnut St., Suite M100, Philadelphia, PA 19107
>   Tel: 215-955-5695
>   Fax: 215-503-3804
>   Email: c_daskalakis@mail.jci.tju.edu
>   Webpage: http://www.jefferson.edu/clinpharm/biostatistics/
>
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