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Re: st: svrest & svresttest commands


From   Nick Winter <nw53@cornell.edu>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: svrest & svresttest commands
Date   Tue, 15 Jun 2004 09:42:58 -0400

At 03:47 PM 6/14/2004 -0700, you wrote:
Hi everyone,
I am using the svrmean command to calculate the mean of variable by race and
gender.  I then want to see if difference in mean between males and females
among whites is significantly different from the gender difference in other
races.  I gather that fro this I need to use the svrest and svresttest
commands.  However, I do not know how to access the mean values after the
estimation command and do the test.  This is what I am doing (0 and 1 stand
for males and females respectively):
. svrest "svrmean usc, by (smallrace pcpreq)"
"[white]0-[white]1-[latino]0+[latino]1"
error when command executed on original dataset
invalid syntax
r(101);
Please help.
Thanks.
Arpita
Greetings,

As author of these programs, I'll take a crack at this.

I think in this case you don't actually need -svrest-, since you can use -svrmean- to get the basic means and their (co)variances. -svrest- is designed to let you do replication-based variance estimation for models and commands that don't have prepackaged svr-based programs already; this is not the case for means. (Think heckman, or user-written -nl- programs, etc.)

So in this case you can just use -svrmean-, followed by -test-:

. svymean usc, by(smallrace pcpreq)
. test [usc]1-[usc]2-[usc]3+[usc]4=0

(You will need to look at the handy key provided by -svrmean- to get the mappings between values of your by() variables and the values 1, 2, 3 and 4 displayed in the output).

Note also that -test- now recognizes the fact that the previous command was a -svy-command, so there is no need for -svytest-; my -svr- commands masquerade as -svy- commands in this context, so the adjusted test gets done.

--Nick Winter

--------------------------------------------------------
Nicholas Winter 607.255.8819 t
Assistant Professor 607.255.4530 f
Department of Government nw53@cornell.edu e
308 White Hall falcon.arts.cornell.edu/nw53 w
Cornell University
Ithaca, NY 14853-4601
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