Question

1. A research study was conducted to examine the clinical efficacy of a new antidepressant before being placed on the market. 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 a depression inventory. The higher the score the more depressed the patient. The data are presented below.

Placebo	Low Dose	Moderate Dose
38	22	14
47	19	26
39	8	11
25	23	18
42	31	5

1. What are the independent and dependent variables?
2. Calculate the accountable, unaccountable and total variation.
3. Can cause and effect statements be made? Explain.

Answer 1

(a) The independent variable is 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.

The dependent variable is the clinical efficacy of a new antidepressant.

(b) The accountable variation = 65.25%

The unaccountable variation = 100 - 65.25% = 34.75%

Total variation = 100%

(c) A cause and effect statement cannot be made since the groups are given a dose of medicine and analyzed solely on the medication effects.