Problem 5 in chapter 11 showed that millennials who read more Harry Potter books tended to be more liberal than those who read less. But does reading Harry Potter cause people to become more liberal? Imagine that we analyzed the relationship between reading Harry Potter and political ideology, with the addition of parents’ political ideology as a control variable, as shown in Table 13.21.

c. Explain in words what each model in Figure 13.28 proposes about how the three variables are related.

d. Tables 13.22 and 13.23 show a sample of adults’ physical activity by appreciation of team work and self-esteem, respectively. Based on the data shown in these tables, identify which of the models in Figure 13.28 cannot accurately represent the relationship among the three variables. Explain why.