Janet,
that indeed is a very frequently asked question :)). I've just posted
a response to a very similar one yesterday.
For the first part, you would use _b[x], as long as -svymean- is an
estimation command. Also, $S notation probably works, but is totally
obsolete. The modern way is to use e(N) for the first one... and as
for the second one, I would probably do
mat DEFF = e(deff)
and then look at the entries of that matrix.
For the second part, you would indeed use -svymean, by()-, and then
either -test- it or -lincom- it. The syntax is sort of described in
-help test-, but requires some trial and error to get through:
<pre>
. sysuse auto
(1978 Automobile Data)
. svyset [pw=head] , psu(rep)
pweight is headroom
psu is rep78
. svymean price, by(for)
Survey mean estimation
pweight: headroom Number of obs = 69
Strata: <one> Number of strata = 1
PSU: rep78 Number of PSUs = 5
Population size = 207
------------------------------------------------------------------------------
Mean Subpop. | Estimate Std. Err. [95% Conf. Interval] Deff
---------------+--------------------------------------------------------------
price |
Domestic | 6317.291 238.8972 5654.006 6980.576 .2866435
Foreign | 6008.935 262.4074 5280.375 6737.495 .2516833
------------------------------------------------------------------------------
. eret li
scalars:
e(df_r) = 4
e(N) = 69
e(N_strata) = 1
e(N_psu) = 5
e(N_pop) = 207
e(n_by) = 2
macros:
e(cmd) : "svymean"
e(predict) : "svy_x_p"
e(varlist) : "price"
e(complete) : "complete"
e(depvar) : "Mean"
e(label) : "label"
e(by) : "foreign"
e(psu) : "rep78"
e(wexp) : "= headroom"
e(wtype) : "pweight"
matrices:
e(b) : 1 x 2
e(V) : 2 x 2
e(V_db) : 2 x 2
e(est) : 1 x 2
e(error) : 1 x 2
e(_N) : 1 x 2
e(_N_subp) : 1 x 2
e(V_msp) : 2 x 2
e(V_srs) : 2 x 2
e(meft) : 1 x 2
e(deft) : 1 x 2
e(deff) : 1 x 2
functions:
e(sample)
. test [price]Domestic = [price]Foreign
Adjusted Wald test
( 1) [price]Domestic - [price]Foreign = 0
F( 1, 4) = 0.40
Prob > F = 0.5635
. lincom [price]Domestic - [price]Foreign
( 1) [price]Domestic - [price]Foreign = 0
------------------------------------------------------------------------------
Mean | Estimate Std. Err. t P>|t| [95% Conf. Interval]
-------------+----------------------------------------------------------------
(1) | 308.3557 490.2406 0.63 0.563 -1052.771 1669.482
------------------------------------------------------------------------------
.
</pre>
On Tue, 21 Sep 2004 08:51:16 -0400 (EDT), Janet E. Rosenbaum
<[email protected]> wrote:
> Sorry if this is a FAQ, but I didn't see it in a search on the mailing
> list archives or in help or in looking through the FAQ.
>
> Two part question:
>
> 1. Where is there a list of the designations for the output for a command?
> For instance, the example below is on the FAQ. I tried guessing how
> to display the estimate, like _mean[x] and _est[x] to no avail.
>
> svymean x
> Mean | Estimate Std. Err. [95% Conf. Interval] Deff
> ---------+--------------------------------------------------------------------
> x | 7.497354 1.154104 4.925852 10.06886 1.826019
>
> di _se[x]*sqrt($S_E_nobs/S_E_deff[1,1])
> 3.9138278
>
> Also, is there some way just to treat the output as a matrix without the
> names?
>
> 2. Eventually, for y a binary variable, I'd like to do
> svymean x, by(y)
> and ttest whether estimates are equal at the two levels of y.
>
> How would I call the components of this?
>
> Mean Subpop. | Estimate Std. Err. Deff Obs
> ---------------+--------------------------------------------------------------
> x |
> y==0 | 6.252655 .2913123 .9953564 2402
> y==1 | 5.087685 .6354503 1.30706 214
>
> Janet
> --
> Janet Rosenbaum [email protected]
> PhD Candidate in Health Policy, Harvard GSAS
> Harvard Injury Control Research Center, Harvard School of Public Health
> *
> * For searches and help try:
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> * http://www.stata.com/support/statalist/faq
> * http://www.ats.ucla.edu/stat/stata/
>
--
Stas Kolenikov
http://stas.kolenikov.name
*
* For searches and help try:
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