NB. Steele and Torrie (1960) Table 11.2 data

a1b1=: 8.53 1 _1 _1 0 20.53 1 _1 _1 0 12.53 1 _1 _1 0 14  1 _1 _1 0 10.8  1  _1 _1 0
a1b2=: 17.53 1 _1 1 0 21.07 1 _1 1 0 20.8 1 _1 1 0 17.33 1  _1  1 0 20.07 1  _1  1 0
a2b1=: 39.14 1 1 0 _1 26.2  1  1 0 _1 31.33 1 1 0 _1 45.8 1  1 0  _1 40.2  1   1 0 _1
a2b2=: 32   1  1 0  1 23.8  1  1 0  1 28.87 1 1 0 1 25.06 1 1 0  1 29.33  1   1 0  1

ab=: 20 5 $ a1b1 ,a1b2, a2b1, a2b2

Yab=:20 1$, 1 {.|: ab

Xab=:20 4$,|: _4 {.|: ab