Question

A researcher wishes to estimate the proportion of adults who have​ high-speed Internet access. What size sample should be obtained if she wishes the estimate to be within 0.04 with 90​% confidence if ​(a) she uses a previous estimate of 0.32​? ​(b) she does not use any prior​ estimates?

Answer 1

a)

here margin of error E =	0.040
for90% CI crtiical Z          =	1.645
estimated proportion=p=	0.320
required sample size n =	p*(1-p)*(z/E)2=	369.00

b)

here margin of error E =	0.040
for90% CI crtiical Z          =	1.645
estimated proportion=p=	0.500
required sample size n =	p*(1-p)*(z/E)2=	423.00