Question

1. 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.

Placebo	Low Dose	Moderate Dose
38	22	14
47	19	26
39	8	11
25	23	18
42	31
40

1. What type of test should you use to assess differences between these treatments and why? (2 points)

2. Run that test by hand or using SPSS, providing me with copies of your interpreted output. Are the depression ratings equal in the three groups? (4 points)

Answer 1

a. Following are the null and alternative hypotheses

Null hypothesis:

There is no significant difference in depression level between the three groups.

Alternative  hypothesis:

We will use F test to compare the means as there are more than 3 means to compare.

It is concluded that the null hypothesis Ho is rejected. There is significant difference in depression level between the three groups.