Table 4.

Box–Behnken Design (BBD) analysis with experimental and predicted values of tensile strength.

Run	Independent Variables						Tensile Strength (MPa)
	Coded Values			Actual Values			Experimental	Predicted	Residual	Error (%)
	X1	X2	X3	X1	X2	X3
1	−1	0	+1	3	6	72	312.29	312.61	−0.325	−0.102
2	+1	0	−1	9	6	24	226.85	226.53	0.325	0.141
3	0	−1	−1	6	3	24	263.74	260.42	3.32	1.259
4	0	0	0	6	6	48	298.89	298.86	0.03	0.010
5	−1	−1	0	3	3	48	276.98	278.17	−1.19	−0.430
6	0	+1	+1	6	9	72	306.08	309.40	−3.32	−1.085
7	0	−1	+1	6	3	72	339.27	337.75	1.52	0.448
8	+1	−1	0	9	3	48	260.13	263.77	−3.64	−1.399
9	0	0	0	6	6	48	301.52	298.86	2.66	0.882
10	0	0	−1	6	9	24	251.55	253.07	−1.52	−0.604
11	0	0	0	6	6	48	297.25	298.86	−1.61	−0.542
12	+1	0	+1	9	6	72	304.92	302.79	2.13	0.699
13	−1	0	−1	3	6	24	253.09	255.22	−2.13	−0.842
14	0	0	0	6	6	48	300.45	298.86	1.59	0.529
15	0	0	0	6	6	48	296.19	298.86	−2.67	−0.901
16	+1	+1	0	9	9	48	242.25	241.06	1.19	0.491
17	−1	+1	0	3	9	48	268.82	265.18	3.64	1.354