Recall Exercise 16.6 where a statistics practitioner analyzed the relationship between the length of a commercial and viewers’ memory of the commercial’s product. However, in the experiment not only was the length varied but also the type of commercial. There were three types: humorous (1), musical (2), and serious (3). The memory test scores, lengths, and type of commercial (using the codes in parentheses) were recorded.

a. Perform a regression analysis using the codes provided in the data file.

b. Can we infer that the memory test score is related to the type of commercial? Test with = .05.

c. Create indicator variables to describe the type of commercial and perform another regression analysis.

d. Repeat part (b) using the second model.

e. Discuss the reasons for the differences between parts (b) and (d).