data pygm;
  infile '/home/pdixon/WWW/stat401b/data/collard.txt' firstobs = 2;
  input clarify $ size $ conc;

proc glm;           
  class clarify size;
  model conc = clarify size size*clarify;
  
  title 'Fit model with interaction';
  lsmeans clarify size size*clarify/stderr;
  means clarify size size*clarify;
  
  estimate 'diff btwn clarify trt' clarify 1 -1;
  estimate 'diff btwn size trt' size 1 -1;
  estimate 'size*clarify int' size*clarify 1 -1 -1 1;

proc glm;           
  class clarify size;
  model conc = clarify size ;
  
  title 'Fit model without interaction';
  lsmeans clarify size /stderr;
  means clarify size;
  
  estimate 'diff btwn clarify trt' clarify 1 -1;
  estimate 'diff btwn size trt' size 1 -1;