Chapter 4.2, Problem 47E

(a)

To determine

To find out the explanatory variable and the response variable in the study.

Answer to Problem 47E

The time children spent in the child care as infants is the explanatory variable and the aggression at an older age is a response variable.

Explanation of Solution

In this study, the infants are followed through their sixth year in school to find out that more time the children spent in child care affect the nature of the children i.e. is this makes the children more assertive or disobedient or aggressive or not. Thus, we can say that the time spent in the child care is the independent variable whereas the aggression at the older age is the dependent variable as it depends on the time spending. Therefore, the time children spent in the child care as infants is the explanatory variable and the aggression at an older age is a response variable.

(b)

To determine

To find is this an observational study or an experiment and explain.

Answer to Problem 47E

The study is an observational study.

Explanation of Solution

In the given study, the children were followed through their sixth year in school, but the researchers did not influence the children in any way and thus no treatments were assigned to the children.

The researchers thus did not assign treatments to the children and thus the study is an observational study.

(c)

To determine

To explain does this study show that the child care makes children more aggressive or not.

Answer to Problem 47E

No.

Explanation of Solution

In part (b) we find out that the study is an observational study.

It is not possible to say that if child care is the cause of the infants’ aggressiveness because the result could be affected by the lurking variables. A possible lurking variable is the parents’ temperament, as children tend to have the same temperament as their parents, while the parents’ temperament might also influence their decision in leaving the child in child care.

For the result it is better to use an experiment instead of an observational study because there is less chance of influence of the lurking variable in that case.