When you read published research studies, you will find that many are experimental studies in which one or more variables are manipulated. An example is a study of whether students with windows in their classrooms give their instructors higher evaluations than students with no windows in their classrooms. You could compare these two groups with a t-test, which you studied in Week 4. Perhaps it would be more interesting to have additional levels of "scenery." You might compare instructor evaluations when students are in a class with no windows, a class with windows that look out to a parking lot, a class with windows that look out to a park, or a class with no windows but pictures of windows on the wall. Since you have multiple levels of the factor, scenery, you use an ANOVA instead of a t-test.
This assignment will give you practice interpreting a study with multiple levels of a factor. Since many research studies rely on the ANOVA for analysis, you will enhance your ability to understand the results of research studies that are of interest to you.
To prepare for this assignment:
- Carefully review Chapter 11 in your text.
- Review the PowerPoint for Chapter 11.
- Consider the following study and data:
Katie is studying aggression among adolescent girls. She believes that there is a relationship between the level of interaction a girl has with her mother and her level of aggression. She has identified 5 girls who fall into each of 4 interaction levels and has measured their aggression scores. Her data are given below.
|
No Interaction
|
Low Interaction
|
Moderate Interaction
|
High Interaction
|
|
4
|
4
|
4
|
3
|
|
5
|
6
|
4
|
4
|
|
6
|
5
|
3
|
4
|
|
6
|
4
|
5
|
3
|
|
5
|
5
|
4
|
3
|
The summary table is as follows:
|
Source
|
Sum of Squares
|
df
|
Mean Square
|
F
|
|
Between groups
|
9.75
|
3
|
3.250
|
5.91
|
|
Within groups
|
8.80
|
16
|
0.550
|
|
|
Total
|
18.55
|
19
|
|
|
The assignment (1-2 pages):
- What are the independent variable and the dependent variables?
- Should Katie conduct a between-subjects ANOVA or a within-subjects ANOVA? Explain your answer.
- How many factors are involved in Katie's study?
- How many levels are involved? Name the level(s).
- What are the null and alternate hypotheses?
- Using a = 0.05, what is Fcrit?
- Is the F-test significant?
- Based on your answer about significance, what else should you do and why?