Suppose the President wants an estimate of the proportion of the population who support his current policy toward gun control. The President wants the estimate to be within 0.04 of the true proportion. Assume a 95% level of confidence. The President's political advisors estimated the proportion supporting the current policy to be 0.60.
How large a sample is required?
How large a sample would be necessary if no estimates were available for the proportion that support current policy?
Formula for sample size
n = (z^2pq)/d^2
Given z = 1.96 (95% CI)
p = 0.60
q = 1 - p = 0.40
d = ...
This solution provides formula and calculatins for sample size.