re: st: -xtmixed- and random terms nested within fixed treatment terms?

[Buzz Burhans <wsb2@cornell.edu>]

David, thanks for this. I am looking at it and see if it makes sense to 
me.  I remain unclear as to why the xtmixed does not nest the subjects in 
the treatment, as I believe both SAS Proc Mixed and S-Plus lme do for a 
similar design.

I will look closely at this, and some help I solicited off list, and see if 
it makes sense to me.

Thanks

Buzz Burhans


At 11:32 AM 6/16/2005 -0500, you wrote:

> .
>
> You said:
>
> > Suppose I have subjects assigned to treatment with outcomes
> > measured at repeated occasions, and a covariate.
> This design is a simple one between one within split-plot with a
> covariate. If we ignore the covariate, the ANOVA design would be,
> from http://www.ats.ucla.edu/stat/stata/faq/xtmixed.htm:
>
> /* spf-2.4    subjects nested in a */
> /* between subjects: a             */
> /* within  subjects: b             */
>
> use http://www.ats.ucla.edu/stat/stata/examples/kirk/spf2-4, clear
>
> /* anova code: */ anova y a / s|a b a*b /, repeated(b)
>
> xi3 e.a*e.b
>
> xtmixed y _Ia_2 _Ib_2 _Ib_3 _Ib_4 _Ia2Xb2 _Ia2Xb3 _Ia2Xb4 || s:
>
> test _Ia_2
>
> test _Ib_2 _Ib_3 _Ib_4
>
> /* scale chi^2 as F-ratio to compare with anova */
> display r(chi2)/r(df)
>
> test _Ia2Xb2 _Ia2Xb3 _Ia2Xb4
>
> display r(chi2)/r(df)
>
>
>
> *
> *   For searches and help try:
> *   http://www.stata.com/support/faqs/res/findit.html
> *   http://www.stata.com/support/statalist/faq
> *   http://www.ats.ucla.edu/stat/stata/
Buzz Burhans
wsb2@cornell.edu


*
*   For searches and help try:
*   http://www.stata.com/support/faqs/res/findit.html
*   http://www.stata.com/support/statalist/faq
*   http://www.ats.ucla.edu/stat/stata/