Term Coefficienta Viscosity Overall acceptability Intercept ao 550.47 7.45 X1 (type of plant) a1 -14.67 -0.17 X2 (plant ratio) a2 -115.50* -0.75** X1X2 a12 30 0.035   R2 0.8877 0.5417   F 15.8 2.36   Sig F 0.003 0.1702   S.E. 49.48 0.82   Adeq precision 9.299 3.532

aY = a0 + a1X1 + a2X2 + a12X1X2 * Significant at p ≤ 0.05 **Significant at p ≤ 0.01

Table 8: Response model constants and regression analysis for viscosity and overall acceptability.