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From | Maarten buis <maartenbuis@yahoo.co.uk> |
To | statalist@hsphsun2.harvard.edu |
Subject | Re: st: ST: postestimation test |
Date | Fri, 6 Aug 2010 15:17:11 +0000 (GMT) |
--- On Fri, 6/8/10, Bontempo, Daniel E wrote: > The model showed the interaction of two factors was > significant, and I thought I could use "test" to probe > which pairs of means were actually different. But some > comparisons involving the reference condition do not > work, and I am not sure why the test is giving chisq. > ----- > > . margins condition#ageGrp <snip> > . test 0.condition#1.ageGrp=1.condition#1.ageGrp this test refers to the parameters in your model, not to the table you get from margins. To test the differences in predicted outcomes, you must first specify the -post- option in -margins-. -test- gives you a Chi square statistic because it produces a Wald test of possibly multiple constraints, in which case it cannot use the normal distribution as the sampling distribution of the test statistic. Hope this helps, Maarten -------------------------- Maarten L. Buis Institut fuer Soziologie Universitaet Tuebingen Wilhelmstrasse 36 72074 Tuebingen Germany http://www.maartenbuis.nl -------------------------- * * For searches and help try: * http://www.stata.com/help.cgi?search * http://www.stata.com/support/statalist/faq * http://www.ats.ucla.edu/stat/stata/