Optimization of Essential Oil Extraction from Bitter Leaf (Vernonia Amygdalina) by Using an Ultrasonic Method and Response Surface Methodology

Table 3

Response surface model adequacy and analysis of variance (ANOVA) for a yield of EO.

Response	Std. dev.	C.V. %	R ^2	Adjusted R^2	Predicted R^2	Adeq precision	Suggested model
Yield of EO	0.0464	1.29	0.9960	0.9909	0.9476	40.3731	Quadratic vs. 2FI
Source	Sum of squares	Mean square		F-value	value
Model	3.78	0.4200		195.33	<0.0001		Significant
A	0.0189	0.0189		8.80	0.0209
B	0.1198	0.1198		55.73	0.0001
C	1.48	1.48		686.43	<0.0001
AB	0.0192	0.0192		8.92	0.0203
AC	0.1665	0.1665		77.43	<0.0001
BC	0.0493	0.0493		22.92	0.0020
A^2	0.8391	0.8391		390.31	<0.0001
B^2	0.2812	0.2812		130.79	<0.0001
C^2	0.6182	0.6182		287.55	<0.0001
Residual	0.0150	0.0021
Lack of fit	0.0122	0.0041		5.59	0.0649		Not significant