Table 2.

Coded values and actual values of factor X ₁ and factor X ₂.

Coded Values	Actual Values
	Factor X 1	Factor X 2
−1	10	4
0	15	6
+1	20	8

X ₁: concentration of PVA (% w/v of film forming gel).

X ₂: number of freeze/thaw cycles.

X ₁ and X ₂ are independent variables.

The dependent variables are Y ₁, Y ₂, and Y ₃, where Y ₁ is time required for 50% drug release;

Y ₂ is percent of drug release at 8th hour;

Y ₃ is “k” of zero order equation.