Table 1: Factors and factor levels investigated in plackett burman experimental design.

Factors Levels
  -1 +1
(A)  Millimole(mM) of surfactant and cholesterol 10 30
(B)  Surfactant:cholesterol ratio 1:1 7:1
(C)  Time of hydration (hr) 0.5 1
(D)  pH of hydration medium 6.8 7.4
(E)  Hydration  temperature (°C) 55 65
(F)  Speed of rotation (rpm) 60 80