Psychologists had a hypothesis that meditatio reduces work stress. Work stress is commonly measured by the Psychological Strain Questionnaire (PSQ). The higher the PSQ score, the less stress the subject feels.
They randomized 200 full-time employees between a treatment group and a control group. The treatment group
was instructed to meditate for about 15 minutes twice per day over a period of 8 weeks. The subjects' PSQ
scores were gathered just before and right after the treatment period,
The results of the experiment showed that the mean change in PSQ scores of the treatment group is 15 points
greater than the mean change in PSQ scores of the control group. To test whether the results could be explained
by random chance, the researchers created the table below, which summarizes the results of 1000 re-
randomizations of the data (with differences between means rounded to the nearest 3 points)
According to the simulations, what is the probability of the treatment group's mean being higher than the
control group's mean by 15 points or more?
Cm be