Table 4. Comparison of Experimental and Predicted Values Using the Box-Behnken Design for the Four Independent Variables on the Content of Polyphenol from Aqueous Ethanol Extraction.

	extraction temperature (°C)	extraction time (min)	solvent composition (%)	liquid–solid ratio	experimental value (%)	predicted value (%)
test N	T	t	C	V	content	eq 2
1	60	90	20	20	12	15.15
2	60	90	100	20	12	15.47
3	60	90	60	20	10	15.31
4	50	120	40	25	19	12.58
5	60	150	60	20	14	17.77
6	60	90	60	20	13	15.31
7	70	120	40	25	14	20.16
8	70	120	80	15	16	16.31
9	60	90	60	10	13	11.90
10	70	60	40	25	19	19.50
11	50	120	40	15	10	10.97
12	50	120	80	15	20	13.53
13	80	90	60	20	13	16.89
14	50	60	80	25	19	14.48
15	60	30	60	20	18	12.85
16	70	60	80	25	17	17.26
17	70	60	40	15	14	14.29
18	50	120	80	25	15	15.14
19	70	60	80	15	10	12.05
20	60	90	60	30	16	18.72
21	40	90	60	20	16	6.53
22	60	90	60	20	15	15.31
23	50	60	40	15	13	6.71
24	50	60	40	25	19	11.92
25	50	60	80	15	12	9.27
26	70	120	40	15	15	18.55
27	70	120	80	25	17	17.92
28	60	90	60	20	12	15.31