Researchers Gawin et al. (Journal of American Medical Association Psychiatry, 1989) reported a study where each of 72 cocaine abusers were randomly assigned to receive one of three treatments for six weeks: 24 subjects received the antidepressant drug desipramine hydrochloride, 24 subjects received lithium carbonate (the usual treatment), and the remaining 24 received a placebo. Forty-one percent of the desipramine group had a relapse during the six week period, compared to 75% for the lithium carbonate and 83% for the placebo.

a. Use the above information to create a well-labeled table of observed cell counts.

b. Is this an experiment or an observational study? How are you deciding?

c. Identify the observational units.

d. Identify the explanatory and response variables. Also, for each variable, identify whether it is categorical or quantitative.

e. State the appropriate null and alternative hypotheses in words.

f. Explain why it would NOT be okay to use the theory-based method to find a p-value for this study.

g. Describe how one might use everyday items (for example, coins, dice, cards, etc.) to conduct a tactile simulation-based test of the hypotheses. Be sure to clearly describe how the p-value will be computed from the simulation.

h. Use an appropriate applet (for example, the Multiple Proportions applet) to find and report the following from the data: (i) the name of a statistic and its numeric value and (ii) the simulation based p-value.

i. Interpret the p-value in the context of the study.

j. State a complete conclusion about this study, including significance, causation, and generalization. Be sure to explain how you are arriving at your conclusion.