INFERENTIAL STATISTICS EXERCISE

Read through the brief description of each of the studies below and answer the corresponding questions.

Study 1

A behavioral psychologist conducts an experiment to determine whether operant conditioning techniques can be used to improve balance in people who consider themselves "clumsy." She recruits 50 participants, each of whom responds yes to the question "Do you consider yourself clumsy?" on a pre-experimental questionnaire. Half the participants are given a balance task (stand on one foot with your arms in the air) with the time they can balance recorded. They are then excused and asked to return 3 weeks later. The other half of the participants are given 3 weeks of operant training during a balance exercise. In this training, the participants are asked to perform the balance task described above. Each time they can beat their previous balance time, they receive $10. After the 3-week period, all participants are asked to perform the balance task again. Alpha is set at 0.05. The members of the training Group can balance for an average of 25 seconds. Members of the Control Group (who did not receive the training) can balance for an average of 24.3 seconds. When the inferential statistical test is conducted on these data, p = 0.08.

What is the IV for this study? The DV?

What is the alternative hypothesis?

What is the null hypothesis?

What population is being tested in this study?

Is the difference observed in the study statistically significant? Why or why not?

Based on your answer to (5) above, what decision should be made about the null hypothesis?

In the context of this experiment, what exactly is p the probability of?

Study 2

Some have claimed that children of divorced parents are not as well adjusted as children of parents who are married. To test this idea, you set up a study with two groups. One group consists of 100 children who have divorced parents. The other group consists of 100 children who have married parents. Each child in the study is asked to complete the Social Adjustment Scale for Children (SASC). Higher scores on the scale indicate better social adjustment.

1. Does this study contain an independent variable? Why or why not?

2. What dependent variable is measured in this study?

3. What is the null hypothesis for this study?

4. What is the alternative hypothesis?

The results indicate a mean difference of 10 on the SASC scale between the two groups of children. With alpha set at .05, p = .02.

5. What decision should be made with regard to the null hypothesis?

6. Describe one possible source of bias that could be present in this study causing the results that were observed.