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st: test or ftest command


From   Lisa Marie Yarnell <lisayarnell@yahoo.com>
To   statalist@hsphsun2.harvard.edu
Subject   st: test or ftest command
Date   Wed, 8 Jun 2011 10:28:58 -0700 (PDT)

Hello Stata group!  I am trying to do an ftest (or other test possibly using the "test" command) comparing two models: one regression model in which clustering of persons within schools is modeled, and one regression with clustering of persons within schools *not* modeled.  

I am concerned that these are not really nested models, however.  Can I still use the test or ftest command?  Is there another command that I should be using?  Our basic question is: "Is it important to model the clustering of persons wihtin schools, based on comparisons of model fit?"  Here are the models: 

(1) regress w3bmi_ms bio_sex w3_yrs w1faminc black hispanic mothed selfed sup_dens ffchdens nat_dens con_dens veg_dens act_dens med_hval, cluster (scid)

(2) regress w3bmi_ms bio_sex w3_yrs w1faminc black hispanic mothed selfed sup_dens ffchdens nat_dens con_dens veg_dens act_dens med_hval

Can I use the test command for this?  When I tried, I got the error message below; Stata treated "cluster(scid)" as a variable in the model:

regress w3bmi_ms bio_sex w3_yrs w1faminc black hispanic mothed selfed sup_dens ffchdens nat_dens con_dens veg_dens act_dens med_hval, cluster (scid)

test cluster(scid)
cluster not found

THANKS!
Lisa
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