Is there a difference in the variance of 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.

Source: Data extracted from “Carrier Ratings: Why It Pays to Think Small,” Consumer Reports, February 2016, p. 51.

a. At the 0.05 level of significance, is there evidence of a difference in the variability of the satisfaction rating between the types of cellphone providers?

b. Determine the p-value in (a) and interpret its meaning.

c. What assumption do you need to make in (a) about the two populations in order to justify your use of the F test?

d. Based on the results of (a) and (b), which t test defined in Section 10.1 should you use to compare the mean satisfaction rating of the two types of cellphone providers?