where μ is the overall mean; τi the effect of the ith level
of factor-A; βj the effect of the jth level of factor-B; γk the
effect of the kth level of factor-C; (τβ)ij the effect of the
interaction between τi and βj; (τγ)ik the effect of the inter-action between τi and γk; (βγ)jk the effect of the interaction
between βj and γk; (τβγ)ijk is the effect of the interaction
among τi, βj and γk; and εijkl is a random error
component.