A student was interested in comparing textbook prices at two universities. She matched the textbooks by subject and compared prices from the University of California at Santa Barbara (UCSB), which is on the quarter system (10 weeks) and California State University at Northridge (CSUN), which is on the semester system (16 weeks).
a. Test the hypothesis that the books for UCSB tend to cost less than the books for CSUN, using a significance level of 0.05. For 17 of the pairs the prices were higher at CSUN, and for 7 of the pairs they were higher at UCSB. There were no ties.
b. Why is the sign test probably a good choice for these data?