Table 2.

3² Full factorial design for the preparation of batches.

Formulation no.	Coded levels
	Variable 1	Variable 2
I	−1	−1
II	−1	0
III	−1	+1
IV	0	−1
V	0	0
VI	0	+1
VII	+1	−1
VIII	+1	0
IX	+1	+1