Question

The First National Bank of Wilson has 680 checking account customers. A recent sample of 60 of these customers showed 21 have a Visa card with the bank.


Construct the 90% confidence interval for the proportion of checking account customers who have a Visa card with the bank. (Use z Distribution Table.) (Round your answers to 3 decimal places.)

Answer 1

sample success x=				21
sample size n=				60
sample proportion p̂ =x/n=				0.3500
population size N=				680
std error Se =(√(p*(1-p)/n))*(√((N-n)/(N-1))=				0.0588
for 90 % CI value of z=				1.645
margin of error E=z*std error                            =				0.097
lower confidence bound=p̂-E=				0.253
upper confidence bound=p̂+E=				0.447

0% confidence interval for the proportion =(0.253 , 0.447)