How do the ratings of TV and phone services compare? The file Telecom contains the rating of

Question:

How do the ratings of TV and phone services compare? The file Telecom contains the rating of 13 different providers. (Data extracted from "Ratings: TV, Phone, and Internet Services," Consumer Reports, May 2012, p. 25.)
a. At the 0.05 level of significance, is there evidence of a difference in the mean service rating between TV and phone services?
b. What assumption is necessary about the population in order to perform this test?
c. Use a graphical method to evaluate the validity of the assumption in (a).
d. Construct and interpret a 95% confidence interval estimate of the difference in the mean service rating between TV and phone services.
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