An automobile manufacturer would like to know what proportion ofits customers are not satisfied with the service provided by thelocal dealer. The customer relations department will survey arandom sample of customers and compute a 90% confidence intervalfor the proportion who are not satisfied.
(a) Past studies suggest that this proportion will be about0.21. Find the sample size needed if the margin of the error of theconfidence interval is to be about 0.025.
(You will need a critical value accurate to at least 4decimal places.)
Sample size:
(b) Using the sample size above, when the sample is actuallycontacted, 29% of the sample say they are not satisfied. What isthe margin of the error of the confidence interval?
