1.6 The Mercer–Hall wheat data are given in Table 1.7 as a 20 × 25 matrix. Suppose b[1] and b[2] are two integers dividing 20 and 25, respectively. Partition the original matrix into b[1] × b[2] blocks and average the data values over each block to get an aggregated matrix of size n[1]∕b[1] × n[2]∕b[2].

Table 1.8 gives five choices for the dimensions (b[1], b[2]) with the size given by b = b[1]b[2]