Statistics
posted by Megan .
A researcher wishes to estimate the proportion of adults who have highspped internet access. What size sample should be obtained if she wishes the estimate to be within .02 with 90% if
A) She uses a previous estimate of 0.48?
B) She does not use any prior estimates?
Please help!!!!!!!!!!

Formula to find sample size:
n = [(zvalue)^2 * p * q]/E^2
... where n = sample size, zvalue is found using a ztable for 90% confidence (which is 1.645), p = .48 (when no value is stated in the problem p = .50), q = 1  p, ^2 means squared, * means to multiply, and E = .02.
Plug values into the formula and calculate n.
I hope this will help get you started. 
THANK YOU

A researcher wishes to estimate the proportion of adults who have highspped internet access. What size sample should be obtained if she wishes the estimate to be within 1% of true proportion

How do you know what the zvalue is? I've never used a ztable.