15.18 Comparing smartphone sales Refer to the previous exercise.

a. Would the results of your analysis change if the second value under the sales with discount column be 9 instead of 25? What does this illustrate about the analysis?

b. Suppose the retailer actually wanted to compare smartphone sales without discount or a gift coupon, sales with discount, and sales with a gift coupon. Which significance test could she use for comparison if she did not want to assume that the sales have a normal distribution for each of the above three categories?