Question 474843
The margin of error is approximately given by 

{{{2.575*sqrt(((1/2)(1/2))/n) = 2.575*(1/(2sqrt(n))) = 1.2875/sqrt(n)}}}, where {{{2.575 = z[0.995]}}}

when the parameter p is unknown.  

==> {{{0.005 = 1.2875/sqrt(n)}}}, or n = 66,306.25.
So sample size must be at least 66,307.