Table 1.

Experimental design matrix to screen for variables that determine the extraction yield of shikimic acid from Picea meyeri needles and ANOVA results^a.

Run	BBD experiments				ANOVA
	X 1 (min)	X 2 (W)	X 3 (mL/g)	Y (mg/g)	Source	Sum of squares	Degree of freedom	Mean square	F value	P value
1	40	200	12	17.92	Modelb	15.50	9	1.72	4.63	0.0278c
2	20	200	12	16.51	X 1	3.80	1	3.80	10.21	0.0152c
3	30	200	10	16.80	X 2	0.03	1	0.03	0.09	0.7761
4	20	150	10	15.37	X 3	0.02	1	0.02	0.06	0.8184
5	40	250	10	16.20	X 1 X 2	3.37	1	3.37	9.06	0.0197c
6	40	200	8	17.97	X 1 X 3	0.30	1	0.30	0.80	0.4007
7	30	250	12	16.85	X 2 X 3	6.33	1	6.33	17.02	0.0044c
8	20	250	10	17.24	X 1 2	1.09	1	1.09	2.94	0.1302
9	20	200	8	15.47	X 2 2	0.59	1	0.59	1.59	0.2472
10	30	200	10	15.62	X 3 2	0.05	1	0.05	0.14	0.7200
11	30	150	8	17.83	Residual	2.60	7	0.37
12	40	150	10	18.00	Lack of fit	1.43	3	0.48	1.62	0.3186
13	30	200	10	16.63	Pure error	1.18	4	0.29
14	30	200	10	16.83	Cor. total	18.11	16
15	30	150	12	14.62
16	30	250	8	15.03
17	30	200	10	16.97
					Credibility analysis of the regression equations
					Index mark	Standard deviation	Mean	Coefficient of variation%	R 2	Adequacy precision
					Y	0.61	16.58	3.68	0.8562	7.6139

^aThe results were obtained with Design Expert 7.0 software.

^b X ₁ is the ultrasound irradiation time (min), X ₂ is the ultrasound irradiation power (W), X ₃ is the liquid-solid ratio (mL/g), and Y is the extraction yield (mg/g).

^cSignificant at P < 0.05.