where /_L is the common mean, oi is the effect of factory
i of a number of a, @j the effect of assessor j of a number
of b, OThj the interaction, and k(ij) is the error term
for the k replicate out of a number of c. The replicate is
nested under assessor and factory because all the replicates
numbered k have nothing in common except for
the number. No logical interaction exists between the
replicate and the two factors.