In a recent study of animal-assisted therapy (Cole et al., 2007), researchers investigated whether patients hospitalized with heart failure could be helped by a visit from a dog. Th e 76 patients in the study were randomly assigned to one of three groups: one group received a 12-minute visit from a volunteer and a dog, another group received a 12-minute visit from a volunteer only, and the third group received no visit. Many variables, including heart rate, blood pressure, and anxiety levels, were measured on the patients prior to and aft er the visit.
a. Identify the explanatory variable(s) in this study.
b. Identify the response variable(s) in this study.
c. Is this an experiment or an observational study? Explain.
d. Describe the purpose of randomly assigning patients to treatment groups.
e. Researchers also reported summary information on a variety of background variables such as age, sex of respondent, and smoking status. Do you think the researchers were hoping to find significant differences among the three groups on these variables? Explain why or why not.