extremely significantp < 0.0001
highly significantp < 0.01
As is shown in Table 2 , the analysis of variance showed that this model was significant ( p < 0.01), C and B 2 had extremely significant effects ( p < 0.0001), B and AB had highly significant effects ( p < 0.01) and A, BC and A 2 had significant effects ( p < 0.05).