libname data "C:\Documents and Settings\ejohnson\My Documents\MultilevelModels";

** Variance component model;
proc mixed data=data.popular;
class school;
model popular = / solution;
random intercept / subject = school;run;

** Sex is included as a random effect and teacher experience (texp) as a fixed effect;
proc mixed data=data.popular;
class school;
model popular = texp sex / solution;
random intercept sex / subject=school type=un;
* NOTE: the estimated variances are labeled according to their;
* order in the random statement;
* So UN(1,1) is the random intercept, UN(2,2) is the random sex effect;
run;

* Generate an interaction of sex with teachers experience;
data data;
set data.popular;
gxt = sex*texp;
run;

proc mixed data=data;
class school;
model popular = texp sex gxt / solution;
random intercept sex / subject=school type=un;
run;