Eighty-six patients with bladder cancer participated in a study in which all tumors were removed and then the subjects were monitored to see if the tumors returned. Patients were randomly assigned to one of two treatment groups: one group received a placebo and one group received the drug thiotepa. The study was double-blind. Tumors returned in 29 out of 48 patients in the placebo group and in 18 out of 38 patients in the thiotepa group.

(a) What is the sample in this study? What is the intended population?

(b) What are the variables in this study? Classify each as categorical or quantitative.

(c) Is this an experiment or an observational study? What does it mean to say that the study was ‘‘double-blind”?

(d) What kind of graph or table might be used to display the data? Display the data in this way.

(e) Compute relevant statistics to compare the success rate of the two groups. Does the drug appear to be more effective than the placebo?