Stata The Stata listserver
[Date Prev][Date Next][Thread Prev][Thread Next][Date index][Thread index]

st: lincom and coefficients


From   "Wendell Joice" <wjoice@erols.com>
To   <statalist@hsphsun2.harvard.edu>
Subject   st: lincom and coefficients
Date   Fri, 4 Apr 2003 11:19:16 -0500

Dear Statalist,
Using Stata 7, I am trying to use -lincom- to test some partial interaction
effects after xi:logistic
regression. I would like to compare one of the partial interactions with
another that is part of the reference group. I can't quite figure it out. In
fact, is there a simple explanation on how to use -lincom- to test
interaction factors that are partially obscured by being in the reference
group. The example in the manual uses smokers and race: the reference group
is White nonsmokers. When you want to test a factor that is in the reference
group, say White smokers,  it appears that you use -Black. How does that
work?

More specifically, in my case:

Example: xi: logistic psyment i.racewbh*i.agecatc  i.sex  i.met i.patseen
i.psydin2  i.yearmhp if csample==1, robust cluster(phycoden)

     psyment | Odds Ratio   Std. Err.      z    P>|z|     [95% Conf.
Interval]
      -------------+--------------------------------------------------------
--------
       _Iracewbh_2 |   .5307681   .1412873    -2.38   0.017     .3150069
.8943132
       _Iracewbh_3 |   .6093152   .1890877    -1.60   0.110     .3316578
1.119422
       _Iagecatc_2 |   1.291446   .1788368     1.85   0.065     .9844729
1.694139
       _Iagecatc_3 |   1.179668   .1588651     1.23   0.220     .9060019
1.535998
       _Iagecatc_4 |   .6028866   .0872337    -3.50   0.000     .4540172
.8005692
      _IracXag~2_2 |   1.543127   .4586715     1.46   0.144     .8617767
2.763177
      _IracXag~2_3 |   1.017071   .3300086     0.05   0.958     .5384711
1.921057
      _IracXag~2_4 |   1.295049   .4516837     0.74   0.459     .6537424
2.565465
      _IracXag~3_2 |   1.226491   .4026047     0.62   0.534     .6445417
2.333875
      _IracXag~3_3 |   1.334677   .4433691     0.87   0.385      .696007
2.559402
      _IracXag~3_4 |    1.24216    .504893     0.53   0.594     .5600092
2.755245

etc etc

For example, I want to test _IracXag~2_3_ vs _IracXag~1_3, and _IracXag~3_3
vs _IracXag~1_3, etc....

Since _IracXag~1_3 is partially part of the reference group, how do I make
these tests using
-lincom-?

Is this the best approach for such tests? Should I be using another coding
system via xi2 ...or will that just be extra strain on the brain with
minimal gain? ...smile



*
*   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/



© Copyright 1996–2014 StataCorp LP   |   Terms of use   |   Privacy   |   Contact us   |   What's new   |   Site index