How does cell phone service compare between different cities'.' The data stored in Cell Service represent the rating of Verizon and AT&T in 22 different cities.
a. At the 0.05 level of significance, is there evidence of a difference in the mean cell phone service rating between Verizon and AT&T?
b. What assumption is necessary about the population distribution 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 cell phone service rating between Verizon and AT&T.