Table 3. Results of ANOVA of the central composite design.

Response: number	Df	Sum Sq	Mean Sq	F value	Pr(>F)
Block	1	2.67	2.667	0.1700	0.6813762
First-Order (x1, x2, x3)	3	294.37	98.123	6.2552	0.0007989
Two-way Interaction (x1, x2, x3)	3	121.58	40.528	2.5836	0.0601143
Pure Quadratic (x1, x2, x3)	3	41.33	13.778	0.8783	0.4566396
Residuals	70	1098.07	15.687
Lack of fit	17	376.74	22.161	1.6283	0.0896856
Pure error	53	721.33	13.610
Response: length	Df	Sum Sq	Mean Sq	F value	Pr(>F)
Block	1	1.1882	1.18815	6.0129	0.016699
First-Order (x1, x2, x3)	3	9.4330	3.14434	15.9126	5.471e-08
Two-way Interaction (x1, x2, x3)	3	0.3246	0.10820	0.5476	0.651433
Pure Quadratic (x1, x2, x3)	3	2.4919	0.83063	4.2036	0.008578
Residuals	70	13.8320	0.19760
Lack of fit	17	3.4307	0.20180	1.0283	0.445020
Pure error	53	10.4014	0.19625