The ANOVA for the model is presented in Table 2. By using anF-test, the significance and lack of fit of the model were evaluated.According to ANOVA, the lack of fit was not significant at the 95%confidence level. The F-value of the model (13.91) with a P-valueless than 0.0001 implied that the model was significant. The small P-value and a high coefficient of determination (R2= 0.8903) showedthe suitability of the model for representing the real relationshipamong the variables.