Find n for a 99 confidence interval for p with E 0037 using

Find n for a 99% confidence interval for p with E = 0.037 using an estimate of p = 0.85.

Solution

Given a=1-0.99=0.01, Z(0.005) = 2.58 (from standard normal table)

So n=(Z/E)^2*p*(1-p)

=(2.58/0.037)^2*0.85*(1-0.85)

=619.935

Take n=620