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Re: st: Re: Non parametric repeated measures


From   Ronán Conroy <rconroy@rcsi.ie>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: Re: Non parametric repeated measures
Date   Wed, 23 Aug 2006 18:20:09 +0100

On 23 Lún 2006, at 12:51, Paul Fenner wrote:

I have been asked to analyse the following experiment The outcome score is a bacterial concentration scored 0 to 5. The data consists of an initial score, the score after treatment A and then the score after treatment B. This is measured on 32 subjects. The whole experiment is then repeated on a new set of 25 subjects but this time the sequence is initial, treatment B, treatment A. The null hypothesis is that the removal of bacteria is independent of the treatment sequence.
I have searched the archive but I cannot find a non-parametric repeated measures anova. As an alternative I can show, using the the ranksum test, that there there is no significant difference between the three measures for the two experiments but I am not happy with this as it is ignoring the correlated nature of the data in each experiment.

I have just finished analysing a similar study, with a 5-valued outcome variable, using ordinal logistic regression and -svy- setting the data to take account of the multiple measures per participant. You can specify your analysis of variance model as a regression model - indeed, if you want a short cut to doing this, run an -anova- in Stata with the option -regress- and you will see it written as a regression model. Useful for writing complicated anovas as regressions.



=========
Ronán Conroy
Royal College of Surgeons in Ireland
rconroy@rcsi.ie
+353 (0) 1 402 2431
+353 (0) 87 799 97 95
www.flickr.com/photos/ronanconroy




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