data diet;
  infile '~/WWW/stat401/data/case0501.txt';
  input lifetime trt $;
  
  trt2 = trt;
  if trt in ('N/R40','N/R50','R/R50') then trt2 = 'Reduced';
  
proc glm;
  class trt;
  model lifetime = trt;
  lsmeans trt /stderr;
    
proc glm;
  class trt2;
  model lifetime = trt2;
run;
     
proc glm;
  class trt trt2;
  model lifetime = trt2 trt;
run;

proc glm;
  where trt2 = 'Reduced';
  
  class trt;
  model lifetime = trt;
run;