In a double-blind study, researchers tested whether the antidepressant drug Lu AA21004 lowered depression in adults with major depressive disorder (MDD). A total of 560 MDD adults were randomly assigned to 3 treatment groups of different Lu AA21004 dosages or a placebo group. Those in the treatment groups were given the drug in pill form for 8 weeks. The individuals’ levels of depression were measured using a questionnaire called the Hamilton Rating Scale for Depression (HRSD). The study found that the drug successfully lowers MDD adults’ HRSD scores.
a. Describe the treatment and control groups.
b. Is the study an experiment or an observational study? Explain.
c. What does random assignment mean in this study? How could this be accomplished?
d. Describe the sample and the population.