ANOVA

Imagine that a psychologist working with veterans with post-traumatic stress disorder wants to compare the effectiveness of several therapies focused on reducing symptoms of anxiety. The psychologist randomly sampled 20 veterans who recently returned from combat and randomly assigned each of them to receive one of four interventions for 8 weeks. A survey was used to measure the participants' anxiety at the end of the 8 weeks. Higher anxiety scores indicate more anxiety.

Enter the following dataset into SPSS, then conduct a one-way ANOVA to answer the questions and determine if the type of therapy a veteran receives is related to the amount of anxiety he or she report

Anxiety scores for five veterans who received behavioral therapy: 104, 101, 103, 102, 104

Anxiety scores for five veterans who received cognitive therapy: 101, 102, 101, 105, 103

Anxiety scores for five veterans who received biofeedback therapy: 100, 102, 104, 101, 100

Anxiety scores for five veterans who received medication therapy: 104, 107, 106, 105, 106

1. Before computing any analyses, state the null hypothesis and alternative hypothesis in words (not formulas).
2. Identify the factor and treatment effect.
3. Name the levels of the factor.
4. State the degrees of freedom between groups and explain how you calculated it by hand.
5. State the degrees of freedom within groups and explain how you calculated it by hand.
6. Identify the obtained F value using SPSS and report it in your answer document.
7. Identify the p value using SPSS and report it in your answer document.
8. Explain whether the F test is statistically significant. Explain how you know.
9. Explain what the psychologist can conclude about the relationship between different types of therapy and anxiety.
10. Should the psychologist conduct a post hoc test? Why or why not? If post hoc testing is needed, conduct a Tukey HSD post hoc analysis in SPSS. Explain what the results tell you.