Yij = mu + bi + error

proc import datafile="F:\publish\data analysis using R\data\rail.csv" out=rail dbms=csv replace;
run;

proc mixed data=rail;
  class rail;
  model travel= / s;
  random rail;
run;

proc mixed data=rail method=ml;
  class rail;
  model travel= / s;
  random rail;
run;

* GEE;
proc genmod data=rail;
  class rail;
  model travel = ;
  repeated subject = Rail / type=cs;
run;

proc nlmixed data=rail;
  parms mu=100, s2b=10, s2e=10;
  model travel ~ normal(mu+bi, s2e);
  random bi ~ normal(0, s2b) subject=rail;
run;