The Gallup Organization surveyed 1,252 debit cardholders in the U.S. and found that 180 had used the debit card to purchase a product or service on the Internet. (Card Fax, November 12, 1999.)

a. Describe the population of interest to the Gallup Organization.

b. Is the sample size large enough to construct a valid confidence interval for the proportion of debit cardholders who have used their card in making purchases over the Internet?

c. Estimate the proportion referred to in part b using a 99% confidence interval. Interpret your result in the context of the problem.

d. If you had constructed a 90% confidence interval instead, would it be wider or narrower?