Question

9.1.9) A researcher wishes to estimate the percentage of adults who support abolishing the penny. What size sample should be obtained if he wishes to estimate to be within 3 percentage points with 9% confidence if
a.) he this is a previous estimate of 38%?
b.) he does not use any prior estimates?

Answer 1

(please confirm if confidence is 90% ; as it should not be 9 %)

a)

here margin of error E =	0.03
for90% CI crtiical Z          =	1.645
estimated proportion=p=	0.380
required sample size n =	p*(1-p)*(z/E)2=	709.00

b)

here margin of error E =	0.03
for90% CI crtiical Z          =	1.645
estimated proportion=p=	0.500
required sample size n =	p*(1-p)*(z/E)2=	752.00