A study of child care enrolled 1364 infants and followed them through their sixth year in school. Later, the researchers published an article in which they stated that “the more time children spent in child care from birth to age 4½, the more adults tended to rate them, both at age 4½ and at kindergarten, as less likely to get along with others, as more assertive, as disobedient, and as aggressive.”

a. What are the explanatory and response variables?

b. Is this an observational study or an experiment? Justify your answer.

c. Does this study show that child care makes children more aggressive? Explain your reasoning.