Question

Determine the sample size needed in order to be 95 percent confident the p, the sample proportion of HD television sets that last at least five years without a single repair, is within 0.03 of , the true proportion of sets that last at least five years without a single repair.

I get that:
standard deviation: .03
z = 1.960

so I'm thinking to use:
n = (zo/E)^2
but I'm not getting an answer that makes sense.