Brett Allen

Hi Jag
A suggestion –  have you considered using some corelation studies to define which factors of your DOE have a direct and significant effect on the response. This may help eliminate some of the lesser contributors.

You could use the formula for sample size:
np>5
where n = sample size to inspect
p = probability of (in you case finding a failure) = 0.06
Therefore n > 5/p
n> 5/(0.06) = 84 samples.
Brett.