Consider now equation 4.53 where the model is built in the sequence
X_0, X_3, X_1, and X_2. The sequential sums of squares for X_3, X_1, and
X_2 are R(β_3|β_0), R(β_1|β_0 β_3),and R(β_2|β_0 β_3 β_1).These are different
from the sequential sums of squares obtained in the model 4.52. That is,
the sequential sums of squares are dependent on the order in which the
variables are added to the model. It should be clear from the definition of
the R-notation that the ordering of the parameters after the vertical bar is
immaterial.