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
*
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