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Table 3 Analysis of variance for the experimental results of zerumbone content from Z. zerumbet rhizomes

From: Optimization of microwave-assisted extraction of zerumbone from Zingiber zerumbet L. rhizome and evaluation of antiproliferative activity of optimized extracts

Parameter Estimated coefficient Standard error Degree of freedom Sum of squares F value Prob > F
Model intercept B0 5.51 0.084 14 3.95 13.38 0.0001
Linear
 X1 0.14 0.042 1 0.25 11.74 0.005
 X2 0.017 0.042 1 0.00343 0.16 0.693
 X3 −0.055 0.042 1 0.037 1.77 0.211
 X4 0.27 0.042 1 0.085 40.46 0.0001
Quadratic
 \(X_{1}^{2}\) −0.41 0.063 1 0.89 42.02 0.0001
 \(X_{2}^{2}\) −0.096 0.063 1 0.05 2.35 0.1513
 \(X_{3}^{2}\) −0.085 0.063 1 0.039 1.84 0.2001
 \(X_{4}^{2}\) −0.39 0.063 1 0.081 38.52 0.0001
Interaction
 X1X2 0.12 0.073 1 0.057 2.71 0.1259
 X1X3 0.14 0.073 1 0.079 3.74 0.077
 X1X4 −0.31 0.073 1 0.039 18.45 0.001
 X2X3 0.45 0.073 1 0.08 37.78 0.0001
 X2X4 −0.13 0.073 1 0.072 3.42 0.0894
 X3X4 −0.061 0.073 1 0.015 0.69 0.4212
Lack of fit    10 0.23 2.15 0.3596
Pure error    2 0.022   
Residual    12 0.025   
R2 adjusted      0.875  
R2      0.939  
C.V.% 2.86      
Corr. total    26 4.21   
  1. X1, ethanol concentration; X2, microwave power; X3, irradiation time; X4, liquid-to-solid ratio