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
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Room 33, Emmanuel Kaye Building
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Opinions expressed are those of the author, not of the institution.
-----Original Message-----
From: [email protected] [mailto:[email protected]] On Behalf Of David Airey
Sent: 09 April 2009 18:23
To: [email protected]
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
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