*NKNW768.sas, weighted least squares using data in Table 18.2;
options nocenter;

data a1; infile 'u:\.www\datasets512\CH18TA02.DAT';
   input  strength type;
proc print data=a1; run;

proc means data=a1; 
   var strength;
   by type;
   output out=a2 var=s2;
data a2; set a2; wt=1/s2;

data a3; merge a1 a2; by type; 

proc glm data=a3; 
   class type; 
   model strength=type;
   weight wt; 
run;