The main effect estimates and the interaction effect
estimates are represented in Table 5. The effect is defined as
the difference between the average response of factor at high
level and that of average response of the factor at low level.
The interaction effect between two factors (say, C B) may
be defined as the mean difference between the effects of
“test temperature” at high level of “specimen diameter” and
the effect of “test temperature” at low level of “specimen
diameter”. The full model regression coefficients were
determined in terms of their coded values by MINITAB-15
software [14]. The effect estimates of the factors can be