A drug company developed a new medication to control the manic phase of bipolar manic-depression. The firm hired a hospital psychiatrist to test the effectiveness of the drug. He identified a group of manic-depressive patients and randomly assigned them to a drug or placebo group. Nurse Ratched was told to administer the drug and Nurse Johnson was told to administer the placebo. Each nurse made daily observations of her patients during treatment. A month later the observations were compared. In general, patients in the drug group had behaved more "normally" than patients in the placebo group. The drug company published its product's effectiveness.

• Identify the independent variable(s).

• Identify the dependent variable(s).

• Identify the experimental design.

• Identify the confounding variables, and briefly explain your answer

• Propose a method to improve the study.