Example 4.5.2---- Subvector (Two sample)

x1={12.3,12.1,12.8,12,12.1,11.8,12.7,12.5};
x2={2.5,2.2,2.9,2.1,2.2,1.9,2.9,2.7};
x3={2.9,2.5,3,2.2,2.4,2,3.3,3};
y1={12,11.8,12.7,12.4,12.1,12,11.7,12.2};
y2={2.3,2,3.1,2.8,2.5,2.2,2,2.5};
y3={2.7,2.4,3.6,3.2,2.8,2.7,2.4,3};