Prison Isolation Experiment
(Adapted from problem 7.31)
Subjects from Central Prison in Raleigh, NC, volunteered for an experiment involving an "isolation" experience.
The goal of the experiment was to find a treatment that reduces subjects' psychopathic deviant T scores.
(The "psychopathic deviant T score" measures a person's need for control or their rebellion against control, and it is part of a commonly used mental health test called the Minnesota Multiphasic Personality Inventory MMPI test.)
The experiment had three treatment groups:
Treatment 1: Four hours of sensory restriction plus a 15-minute "therapeutic" tape advising that professional help is available.
Treatment 2: Four hours of sensory restriction plus a 15-minute "emotionally neutral" tape on training hunting dogs.
Treatment 3: Four hours of sensory restriction but no taped message.
Forty-two subjects were randomly assigned to these treatment groups, and an MMPI test was administered before and after the treatment.
Distributions of the differences between pre and post-treatment scores (pre - post) are shown below.
Treatment 1
Treatment 2
Treatment 3
Mean
6.21
2.86
-3.21
SD
12.3
7.94
8.57
n
14
14
14
Compute the p-value for the treatment that produced the greatest reduction in subjects' psychopathic deviant T scores.