# Re: st: RE: How to do domain analysis in svy:reg or svy:glm?

 From Austin Nichols To statalist@hsphsun2.harvard.edu Subject Re: st: RE: How to do domain analysis in svy:reg or svy:glm? Date Mon, 26 Oct 2009 15:17:27 -0400

```For -svy- prefixed estimation, one usually wants the -subpop- option
documented at -help svy-. E.g.
g byte male=(sex==1) if sex<.
svy, subpop(male): reg BMI age

On Mon, Oct 26, 2009 at 2:12 PM, Nick Cox <n.j.cox@durham.ac.uk> wrote:
> I leave all -svy- questions to the savvy, but there's apparently a simple misconception here.
>
> You can get separate regressions by using -by:- as a prefix command. Expecting -by()- and -over()- to work as options is not surprising if you've ingested graphics syntax, but the logic is different for regressions and the syntax certainly is.
>
> by <whatever> : <somecommand>
>
> produces separate results.
>
> <somecommand>, by(<whatever>)
>
> produces composite results. At least it should be something like that.
>
> Nick
> n.j.cox@durham.ac.uk
>
> CHEN HSINJEN
>
> My aim is to do stratified regression analysis while accounting for
> the complex sampling design, i.e. to estimate the relationship between
> BMI and age, separately in women and men.
> However, the "reg" and "glm" commands do not allow "over", or even "by", option.
>
> For example, the following statement is not allowed.
>
>      svy: reg BMI age, over(sex)
>
> Thus, we may want to solve this by using "if":
>
>     svy: reg BMI age if sex == 1 *(for men)
>     svy: reg BMI age if sex == 2 *(for women)
>
> But, the problem is, when sex == 2, some strata have only one cluster
> (or some clusters have only one observations.) And then, the S.E. is
> not estimated by stata.
>
> How can I get unbiased estimate of regression coefficient and its S.E.
> under this circumstance?
> Is this solvable in stata?
>

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