Practice Problems: ANOVA

A research study was conducted to examine the clinical efficacy of a new antidepressant. Depressed patients were randomly assigned to one of three groups: a placebo group, a group that received a low dose of the drug, and a group that received a moderate dose of the drug. After four weeks of treatment, the patients completed the Beck Depression Inventory. The higher the score, the more depressed the patient. The data are presented below. Compute the appropriate test.

1. What is your computed answer?

2. What would be the null hypothesis in this study?

3. What would be the alternate hypothesis?

4. What probability level did you choose and why?

5. What is your F_crit?

6. Is there a significant difference between the groups?

7. If there is a significant difference, where specifically are the differences?
8. Interpret your answer.

A researcher is concerned about the level of knowledge possessed by university students regarding United States history. Students completed a high school senior level standardized U.S. history exam. Major for students was also recorded. Data in terms of percent correct is recorded below for 32 students. Compute the appropriate test for the data provided below.

1. What is your computed answer?

2. What would be the null hypothesis in this study?

3. What would be the alternate hypothesis?

4. What probability level did you choose and why?

5. What were your degrees of freedom?

6. Is there a significant difference between the four testing conditions?

7. Interpret your answer.

8. If you have made an error, would it be a Type I or a Type II error? Explain your answer.

Neuroscience researchers examined the impact of environment on rat development. Rats were randomly assigned to be raised in one of the four following test conditions: Impoverished (wire mesh cage - housed alone), standard (cage with other rats), enriched (cage with other rats and toys), super enriched (cage with rats and toys changes on a periodic basis). After two months, the rats were tested on a variety of learning measures (including the number of trials to learn a maze to a three perfect trial criteria), and several neurological measure (overall cortical weight, degree of dendritic branching, etc.). The data for the maze task is below. Compute the appropriate test for the data provided below.

1. What is your computed answer?

2. What would be the null hypothesis in this study?

3. What would be the alternate hypothesis?

4. What is your F_crit?

5. Are there any significant differences between the four testing conditions?

6. Interpret your answer.