Question

Scenario: 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. You can find the data for this Assignment in the Weekly Data Set forum found on the course navigation menu.

Anxiety scores for 5 veterans who received behavioral therapy
105
102
105
102
106
• Anxiety scores for 5 veterans who received cognitive therapy
113
110
111
107
104
• Anxiety scores for 5 veterans who received biofeedback therapy
100
102
109
100
101
• Anxiety scores for 5 veterans who received medication therapy
107
104
106
105
103

1. Identify the obtained F value using SPSS and report it in your answer document.
2. Identify the p value using SPSS and report it in your answer document.
3. Explain whether the F test is statistically significant. Explain how you know.
4. Explain what the psychologist can conclude about the relationship between different types of therapy and anxiety.
5. 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.

Answer 1

Anxiety scores for 5 veterans who received behavioral therapy = 1

Anxiety scores for 5 veterans who received cognitive therapy = 2

Anxiety scores for 5 veterans who received biofeedback therapy = 3

Anxiety scores for 5 veterans who received medication therapy = 4

Factor	Response
1	105
1	102
1	105
1	102
1	106
2	113
2	110
2	111
2	107
2	104
3	100
3	102
3	109
3	100
3	101
4	107
4	104
4	106
4	105
4	103

Hypothesis:

H₀: All therapies are equally treating anxiety levels.

H₁: Atleast one therapy is treating differently from other therapies.

F value = 4.821

p-value = 0.014

Since p-value is less than level of significance 0.05 we reject null hypothesis and the result is significant.

Since the result is significant the psychologist can conclude that atleast one treatment method is significantly different from the others which means atleast one therapy is significantly reducing the anxiety levels.

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.

Yes he should conduct post hoc test because the ANOVA result is significant.

From the above results we can see that p-value for the comparison between 2-3 groups is 0.011 which is less than level of significance 0.05 hence we conclude that the treatments 2 and 3 are significantly different. And we conclude that treatment 3 i.e., biofeedback therapy is reducing anxiety levels significantly from the other therapies.