Relieving pain with hypnosis. Rehabilitation medicine researchers at the University of Washington investigated whether virtual-reality hypnosis can relieve pain in trauma patients (International Journal of Clinical and Experimental Hypnosis, Vol. 58, 2010). Study participants were 20 patients treated at a major Level 1 trauma center. The patients were randomly assigned to one of three treatment groups: (1) VRH—virtual-reality hypnosis with posthypnotic suggestions for pain reduction, (2) VRD—virtual-reality distraction from pain without hypnotic suggestions for pain reduction, and (3) Control—no virtual-reality hypnosis, but standard care. Pain intensity was measured (on a 100-point scale) prior to treatment and 1 hour after treatment. The differences in pain-intensity levels (before minus after) are listed in the accompanying table.

a. Conduct a nonparametric test to determine whether the distribution of differences in pain-intensity levels differs for the three treatments. Test using a = .05. What do you conclude?

b. Combine the patients in the VRD and Control groups into a single treatment group (called non-posthypnotic suggestion). Compare the VRH treatment patients with the patients in this new group using the appropriate nonparametric test (using a = .05). What do you conclude? VRH VRD Control -20 -12 51 -56 63 21 -34 12 8 0 -7 0 16 29 4 0 -14 -7 -44 43 -11