Optimization of Ultrasound-Assisted Extraction of Flavonoids from Celastrus hindsii Leaves Using Response Surface Methodology and Evaluation of Their Antioxidant and Antitumor Activities

Table 4

Significance of the coefficients in the empirical model.

Model term	Parameter estimate	Standard error	t value^a	value
β0	23.52	0.22	108.17	0.001^b
β1	−0.79	0.11	−7.30	0.001^b
β2	−0.35	0.11	−3.26	0.007^b
β3	−0.32	0.11	−2.98	0.011^b
β4	−0.39	0.11	−3.55	0.004^b
β11	−1.09	0.16	−6.69	0.001^b
β22	−1.65	0.16	−10.14	0.001^b
β33	−2.29	0.16	−14.01	0.001^b
β44	−0.91	0.16	−5.60	0.001^b
β12	−0.40	0.19	−2.14	0.054
β13	−0.01	0.19	−0.04	0.969
β14	0.20	0.19	1.05	0.315
β23	−1.16	0.19	−6.17	0.001^b
β24	−0.25	0.19	−1.31	0.213
β34	0.12	0.19	0.65	0.528

^at_α/2,n-p = t_0.025,12 = 2.18. indicates that the model terms are significant.