A manufacturer of headphones is interested in the sales of a particular headphone model in its stores in 8 airports. Some of these stores are located on the West and some on the East coast of the U.S. Also, the manufacturer recently conducted an advertising campaign. The sales before and after the advertising campaign, which it ran in February using billboards in the airports, are shown below (i.e., data for sales in those stores in January and data for sales in the same stores for March.)
(Some descriptive statistics have also been provided in the table. You will need to decide which ones you need for your calculations in answering the questions below.)
To get full points when answering each part below be sure to: calculate an appropriate statistic, state the result of the test, and state your conclusion.
a) Looking at all the stores, is there a difference in sales between January and March?
b) Did the campaign have a different effect on sales for stores on the East coast versus on the West coast?
c) Was there a difference in sales in January for stores on the East coast versus on the West coast?