Re: st: ttest or xtmelogit?

[David Airey <david.airey@vanderbilt.edu>]

.

Thanks Tiago, Nick and Jeph for your thoughts. I agree with Tiago,  
with his skepticism about the sample size, and Nick for his thoughts  
on the asin(sqrt(proportion)) transformation vs logit transformation.  
Jeph, I'll look at the ICC.

-Dave

On Mar 10, 2008, at 5:39 PM, Jeph Herrin wrote:


> You may want to look at a program I wrote called -clchi2-,
> which is part of the package -cltest- on SSC. This performs
> a chi2 test of independence, adjusted for clustering. It
> implements an adjustment suggested by Donner & Klar (don't
> recall the original paper, but it's in Cluster Randomization
> Trials in Health Services Research, 2000). It needs only 3
> clusters per comparison group to estimate the intra-cluster
> correlation (though it doesn't account for the uncertainty
> in basing the ICC on such a small number of clusters).
>
> hth,
> Jeph
>
>
>
>
> David Airey wrote:
> > .
> > I have a typical pilot data set. Small. I have 12 mice, 6 from one  
> > group, 6 from another. For each mouse I have about 50 yes/no  
> > scores. 50 was enough to get precision on a given mouse. I'm  
> > interested in the group difference. In the past I used xtgee with  
> > mouse as the i(mouse) option, i.e., mouse as the cluster, with  
> > family(binomial) and link(logit). But previously, I did this with  
> > double the number of mice, so I felt I had enough clusters. Here, I  
> > am feeling uncomfortable about the number of clusters (12). The  
> > same goes for xtmelogit, new in Stata 10. Given the number of mice,  
> > is it better to simply transform the summary statistics for animals  
> > (mean of the yes/no vector by animal), like with an arcsine or  
> > logit, and use a ttest?
> > -Dave
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