Is there a difference in the satisfaction rating of traditional cellphone providers who bill for service at the end of a month often under a contract and prepaid cellphone service providers who bill in advance without a contract? The file CellphoneProviders contains the satisfaction rating for 10 traditional cellphone providers and 13 prepaid cellphone service providers.

a. Is there evidence of a difference in the median satisfaction rating for traditional and prepaid providers? (Use α = 0.05.)

b. What assumptions must you make in (a)?

c. Compare the results of (a) with those of Problem 10.9(a) on page 360.