106 Animal-assisted therapy for heart patients. The American Heart Association Conference (Nov. 2005) conducted a study to gauge whether animal-assisted therapy can improve the physiological responses of heart failure patients. A team of nurses from the UCLA Medical Center randomly divided 76 heart patients into three groups.

Each patient in group T was visited by a human volunteer accompanied by a trained dog, each patient in group V was visited by a volunteer only, and the patients in group C were not visited at all. The anxiety level of each patient was measured (in points) both before and after the visits. The accompanying table gives summary statistics for the drop in anxiety level for patients in the three groups. Suppose the anxiety level of a patient selected from the study had a drop of 22.5 points. From which group is the patient more likely to have come? Explain.

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26 Group T: Volunteer Sample Size Mean Drop Std. Dev. 10.5 7.6 + trained dog Group V: Volunteer 25 3.9 7.5 only Group C: Control group (no visit) 25 1.4 7.5 Based on Cole, K., et al. "Animal assisted therapy decreases hemodynamics, plasma epinephrine and state anxiety in hospitalized heart failure patients." American Journal of Critical Care, 2007, 16:575-585.