16. The American Bankers Association collects data on the use of credit cards, debit cards, per- sonal checks, and cash when consumers pay for in-store purchases (The Wall Street Jour- nal, December 16, 2003). In 1999, the following usages were reported. In-Store Purchase Percentage Credit card 22 Debit card 21 Personal check 18 Cash 39 A sample taken in 2003 found that for 220 in-stores purchases, 46 used a credit card, 67 used a debit card, 33 used a personal check, and 74 used cash.

a. Ata = .01, can we conclude that a change occurred in how customers paid for in-store purchases over the four-year period from 1999 to 2003? What is the p-value?

b. Compute the percentage of use for each method of payment using the 2003 sample data. What appears to have been the major change or changes over the four-year period?

c. In 2003, what percentage of payments was made using plastic (credit card or debit card)?