Self Test Answers

These are the answers to the self test on the review page.

a. Dr. A’s design is an experiment.

b. The independent variable is facial expression (smiling versus no expression).

The dependent variable is approaching the toy (measured in distance between the baby and the toy).

c. The treatment condition is the group of babies whose mothers smiled at them. The control condition is the group of babies whose mothers made no facial expression.

d. Dr. A is able to conclude that smiling at babies causes them to change their behavior. Specifically, mothers’ smiling causes babies to approach a toy.

2. Dr. B’s study

a. Dr. B’s study is a correlational design.

b. The scatterplot would look something like this. Note that frequency of massage is on one of the axes and stress is on the other axis. It doesn’t matter which variable you put on which axis.

The frequency of massage could be measured as massages per week, per month, or per year. In any case, the shape of the scatterplot will be the same. In this example, I used massages per month, and it ranges from 0 (low) to 12 (high).

For anxiety, your scale should range from low to high. In this example, I used a range of 0 (low) to 10 (high).

c. Dr. B’s findings mean that as people get massages more frequently, they show less stress. Or you could phrase it as people with greater amounts of stress tend to have massages less frequently. She does not know if massage causes less stress. She cannot say anything about what causes what. There is an association—the two variables are related. Greater stress is associated with less frequent massage (or—more frequent massage is associated with less stress).

3. Dr. C’s study

a. Dr. C did a questionnaire study.

b. Dr. C’s results show how attitudes toward gun control have changed over time. It does not mean that the Sept. 11 attacks caused this change in attitude. We don’t know what caused people’s attitudes about gun control to change. However, policy makers and gun shops might be interested in the data. People might be more receptive to concealed weapons laws, or to allowing a gun shop in their neighborhood.