Re: st: how to handle clustering

[Jeph Herrin <stata@spandrel.net>]

I agree with Michael, if you have 37 classrooms you should start
with a multi-level model. In my experience power estimates for ML
models are rudimentary at best (unless you did a simulation), and
assuming you have the data on hand, you can do better by simply
estimating the model.

cheers,
Jeph

On 7/29/2010 1:52 PM, Michael N. Mitchell wrote:
> Dear Kate
>
> My feeling is that a multi-level model is still an appropriate model,
> because you have data at the child and classroom level, with the
> predictor (intervention) at the classroom level and the outcome at the
> child level.
>
> In any case, I do not feel you will derive more power from using
> -regress- with -vce(cluster classroom)- than you would from using
> -xtmixed .... || classroom:- . In both cases, the standard errors
> reflect the correlation of observations within classrooms, but with the
> multilevel model I feel you would have the opportunity to more clearly
> formulate the model in terms of child level and classroom level predictors.
>
> I hope that helps,
>
> Michael N. Mitchell
> Data Management Using Stata - http://www.stata.com/bookstore/dmus.html
> A Visual Guide to Stata Graphics - http://www.stata.com/bookstore/vgsg.html
> Stata tidbit of the week - http://www.MichaelNormanMitchell.com
>
>
>
> On 2010-07-29 8.36 AM, Kate Welti wrote:
> > Hello,
> >
> > I am analyzing data in which I have treatment and control classrooms
> > (intervention was at the classroom level) and child-level test scores.
> > Ideally, I would use a multi-level model, however, I don't have
> > enough classrooms and children to do so (according to a power
> > analysis). I need to find a way to control for the clustering of
> > children in classrooms. Can Stata's cluster option be used in this
> > instance?
> >
> > Thanks,
> >
> > Kate
> >
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