Stat Help
posted by Shannon .
A researcher wishes to be 95% confident that her estimate of the true proportion of individuals who travel overseas is within 4% if the true proportion. Find the sample necessary if in a prior study, a sample of 200 people showed that 40 traveled overseas last year. If no estimate of the same proportion is available, how large should a sample be????
show your work please so i can understand :P

Try this formula:
n = [(zvalue)^2 * p * q]/E^2
Note: n = sample size needed; use 40/200 for p (convert to a decimal); use 1  p for the value of q. E = maximum error, which is .04 for 4%. Zvalue is found using a ztable (for 95% confidence). Note: ^2 means squared and * means to multiply.
I'll let you take it from here.