Question

A researcher wishes to estimate the percentage of adults who support abolishing the penny. What size sample should be obtained if he wishes the estimate to be within 5 percentage points with 99​% confidence if

​(a) he uses a previous estimate of 28​%?

​(b) he does not use any prior​ estimates?

Answer 1

a)

here margin of error E =	0.050
for99% CI crtiical Z          =	2.576
estimated proportion=p=	0.280
required sample size n =	p*(1-p)*(z/E)2=	536.00

( please try 537 if this comes wrong due to rounding of z score and revert)

b)

here margin of error E =	0.050
for99% CI crtiical Z          =	2.576
estimated proportion=p=	0.500
required sample size n =	p*(1-p)*(z/E)2=	664.00

(try 666 if this comes wrong due to rounding of z score)