DATA COCHRAN; /* reg3.sas  */ ;
* DATA IN THIS EXAMPLE IS FROM P. 274 OF SCHAUM'S 'STAT' by S. GORJI;
 INPUT X1 X2 X3;
XSUM1=(X1 -11.94)**2;
XSUM2=(X2-42.11)**2 ;
YSUM=(Y - 81.28)**2 ;
XXSUM12=(X1 -11.94)*(X2 - 42.11);
XYSUM1=(X1 - 11.94)*(Y -81.28);
XYSUM2=(X2 - 42.11)*(Y - 81.28);
 CARDS;
64 57 8
71 59 10
53 49 6
67 62 11
55 51 8
58 50 7
77 55 10
57 48 9
56 52 10
51 42 6
76 61 12
68 57 9
PROC PRINT;
PROC REG;
MODEL X1=X2 X3;
PROC MEANS SUM;
proc IML;
  A={1765.5   1089.99 ,
     1089.99   3155.78 } ;
  C={3242.43 , 2216.44} ;
  ver=INV(A)  ;
  X=INV(A)*C ;
  Ainver=inv(ver);
  print ver ;
  print X;
  print Ainver;