Table 1.

Experimental matrix of the full factorial design with three center points.

Design	Run order	Coded levels				Uncoded levels
		Independent variables				Independent variables
		T	m	C		T	m	C
						(°C)	(g)	(mg/L)
Factorial design	1	− 1	− 1	− 1	=	30	0.1	10
	2	+ 1	− 1	− 1	=	50	0.1	10
	3	− 1	+ 1	− 1	=	30	0.5	10
	4	+ 1	+ 1	− 1	=	50	0.5	10
	5	− 1	− 1	+ 1	=	30	0.1	70
	6	+ 1	− 1	+ 1	=	50	0.1	70
	7	− 1	+ 1	+ 1	=	30	0.5	70
	8	+ 1	+ 1	+ 1	=	50	0.5	70
Central design	9	0	0	0	=	40	0.3	40
	10	0	0	0	=	40	0.3	40
	11	0	0	0	=	40	0.3	40