# Re: st: stumped with lincom after svymean

 From To statalist@hsphsun2.harvard.edu Subject Re: st: stumped with lincom after svymean Date Tue, 31 Aug 2004 17:04:54 -0400

```Hi Jeff and other Listers -

How about the question 2 of Robert? Below is the question:

>2 - Is it possible to estimate a one-way anova to detect group differences
> with svy commands in Stata 8 based on my above example?

In Robert's example, variable x has three categories: 0, 1, and 2. Is there any way to compare the three group differences concurrently (like a one-way anova) with svy commands?

Hong

----- Original Message -----
Date: Tuesday, August 31, 2004 12:16 pm
Subject: Re: st: stumped with lincom after svymean

> after-svymean, by()-:
>
> > Here is what I am trying to accomplish.  I have a continuous
> variable y, and
> > a categorical variable x.  The categorical variable x has three
> categories:
> > 0, 1, and 2.  I want to test whether y is different among the
> categories of
> > my variable x.  My data are collected using a stratfied, cluster
> design and
> > therefore I must use the survey commands.
> >
> > In previous versions of stata, I would use the code:
> >
> > svymean y, by(x)
> > svytest [x]0=[x]1
> >
> > Stata 8 says that svytest no longer exists and that I should use
> the lincom
> > command.  Maybe the coffee hasn't set in, but I cannot figure
> out how to do
> > replicate the above code using the lincom command based on the
> information
> > from Stata's help screen.
> >
> > So my question is two-fold:
> > 1 - How do I test group differences using the svy command in
> Stata 8 based
> > on my above example?
> > 2 - Is it possible to estimate a one-way anova to detect group
> differences
> > with svy commands in Stata 8 based on my above example?
>
> Here is an example using the auto data (not that I remove the
> labels so that
> my example appears closer the one above):
>
> 	. sysuse auto, clear
> 	. label drop _all
> 	. svyset, srs
> 	. svymean mpg, by(foreign)
> 	. test [mpg]0 = [mpg]1
>
> When the -by()- option is supplied to -svymean-, the name of the
> variable that
> we are taking the mean of becomes something like an equation
> identifier when
> used with -test-.  The values of the categories in the -by()-
> variable are
> used to identify which mean we are talking about.
>
> Here is the output from the above example:
>
> ***** BEGIN:
> . sysuse auto, clear
> (1978 Automobile Data)
>
>
> . label drop _all
>
>
> . svyset, srs
> simple random sample (SRS)
>
>
> . svymean mpg, by(foreign)
>
>
> Survey mean estimation
>
>
> pweight:  <none>                                  Number of obs
> =        74
> Strata:   <one>                                   Number of strata
> =         1
> PSU:      <observations>                          Number of PSUs
> =        74
>                                                  Population size
> =        74
>
>
> -------------------------------------------------------------------
> -----------
> Mean   Subpop. |   Estimate    Std. Err.   [95% Conf. Interval]
>    Deff
> ---------------+---------------------------------------------------
> -----------
> mpg            |
>    foreign==0 |   19.82692    .6558681    18.51978    21.13407
>       1
>    foreign==1 |   24.77273    1.386503    22.00943    27.53602
>       1
> -------------------------------------------------------------------
> -----------
>
>
> . test [mpg]0 = [mpg]1
>
>
>
>
> ( 1)  [mpg]0 - [mpg]1 = 0
>
>
>       F(  1,    73) =   10.40
>            Prob > F =    0.0019
> ***** END:
>
> --Jeff
> *
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> *   http://www.stata.com/support/faqs/res/findit.html
> *   http://www.stata.com/support/statalist/faq
> *   http://www.ats.ucla.edu/stat/stata/
>

*
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```