* Analysis of Covariance with Two Covariates;

data twocov;



 y   a   z1   z2   a1   a2   a3   z11   z12   z13   z21   z22   z23

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 3   1    6    2    1    0    0    6     0     0     2     0     0

 2   1    6    2    1    0    0    6     0     0     2     0     0

 3   1    5    2    1    0    0    5     0     0     2     0     0

 3   1    4    4    1    0    0    4     0     0     4     0     0

 4   1    3    5    1    0    0    3     0     0     5     0     0

 5   1    3    5    1    0    0    3     0     0     5     0     0

 5   1    2    6    1    0    0    2     0     0     6     0     0

 6   1    2    5    1    0    0    2     0     0     5     0     0

 5   2    5    2    0    1    0    0     5     0     0     2     0

 6   2    5    1    0    1    0    0     5     0     0     1     0

 8   2    3    2    0    1    0    0     3     0     0     2     0

 8   2    2    7    0    1    0    0     2     0     0     7     0

 7   2    1    8    0    1    0    0     1     0     0     8     0

 9   2    1    7    0    1    0    0     1     0     0     7     0

 5   3    4    3    0    0    1    0     0     4     0     0     3

 7   3    1    1    0    0    1    0     0     1     0     0     1

 8   3    1    6    0    0    1    0     0     1     0     0     6

 7   3    2    6    0    0    1    0     0     2     0     0     6