Contrast bath treatments use the immersion of an injured limb alternately in water of two contrasting temperatures. Those who use the method claim that it can reduce swelling. Researchers compared...

Contrast bath treatments use the immersion of an injured limb alternately in water of two contrasting temperatures. Those who use the method claim that it can reduce swelling. Researchers compared three treatments: (1) contrast baths and exercise, (2) contrast baths alone, and (3) exercise alone. (Source: R. G. Janssen, D. A. Schwartz, and P.F. Velleman “A Randomized Controlled Study of Contrast Baths on Patients with Carpal Tunnel Syndrome.” Journal of Hand Therapy, 2009). They report the following boxplots comparing the change in hand volume after treatment:

a) The researchers conclude that the differences were not statistically significant. Explain what that means in context.

 b) The title says that the study was randomized and controlled. Explain what that probably means for this study.

 c) The study did not use a placebo treatment. What was done instead? Do you think that was an appropriate choice? Explain.