A research study was conducted to examine the clinical efficiency of a new antid
ID: 3380471 • Letter: A
Question
A research study was conducted to examine the clinical efficiency 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 Back Depression Inventory. The higher the score, the more depressed the patient. The data is presented below. Compute the appropriate test.
Placebo
Low Dose
Moderate Dose
38
22
14
47
19
26
39
8
11
25
23
18
42
31
5
What would be the null & alternate hypothesis?
What probability level did you choose and why?
What is your F critical?
Is there a significant difference between the groups?
If there is a significant difference, where specifically are the differences?
Placebo
Low Dose
Moderate Dose
38
22
14
47
19
26
39
8
11
25
23
18
42
31
5
Explanation / Answer
Sol)
1) Null hypothesis: There is no difference between means of all the groups
Alternative hypothesis: There is a difference between means of all the groups
2) Level of signifiacnce: 5% level
3) Test Statistics:
We use F statistic
From Excel
Conclusion: F cal=11.267 and f crtical value at 5% level =3.885
4) F cal > F critical value at 5% level of significance. We reject the null hypothesis.
Hence There is a significant difference between the groups
Anova: Single Factor SUMMARY Groups Count Sum Average Variance Placebo 5 191 38.2 66.7 Low Dose 5 103 20.6 69.3 Moderate Dose 5 74 14.8 61.7 ANOVA Source of Variation SS df MS F P-value F crit Between Groups 1484.933 2 742.4667 11.26657 0.001761 3.885294 Within Groups 790.8 12 65.9 Total 2275.733 14Related Questions
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