Table 2.

The five-level experimental design of the three additives, Bi₂O₃, TiO₂, and Sb₂O₃, as ceramic initial powders used in ZnO-based low-voltage varistor. The data was presented by coded and actual values.

Run	Type	Coded variable			Actual variable			Y (alpha)
		A	B	C	Bi2O3	TiO2	Sb2O3	Actual value	Predicted value
1	Factorial	−1	−1	−1	0.3	0.3	0.2	7.19	7.10
2	Factorial	+1	−1	−1	0.7	0.3	0.2	6.62	5.82
3	Factorial	−1	+1	−1	0.3	0.7	0.2	4.82	4.55
4	Factorial	+1	+1	−1	0.7	0.7	0.2	3.45	3.46
5	Factorial	−1	−1	+1	0.3	0.3	0.4	6.97	6.42
6	Factorial	+1	−1	+1	0.7	0.3	0.4	5.95	5.67
7	Factorial	−1	+1	+1	0.3	0.7	0.4	3.65	3.90
8	Factorial	+1	+1	+1	0.7	0.7	0.4	3.80	3.34
9	Axial	−1.682	0	0	0.2	0.5	0.3	7.36	7.49
10	Axial	+1.682	0	0	0.9	0.5	0.3	5.29	5.94
11	Axial	0	−1.682	0	0.5	0.2	0.3	6.77	7.53
12	Axial	0	+1.682	0	0.5	0.9	0.3	3.41	3.43
13	Axial	0	0	−1.682	0.5	0.5	0.1	3.51	3.94
14	Axial	0	0	+1.682	0.5	0.5	0.5	2.91	3.26
15	Central	0	0	0	0.5	0.5	0.3	8.93	9.10
16	Central	0	0	0	0.5	0.5	0.3	9.30	9.10
17	Central	0	0	0	0.5	0.5	0.3	9.39	9.10
18	Central	0	0	0	0.5	0.5	0.3	9.83	9.10
19	Central	0	0	0	0.5	0.5	0.3	8.85	9.10
20	Central	0	0	0	0.5	0.5	0.3	8.46	9.10