or
Walter studies stress management techniques. He is testing a new technique for preventing headaches.
Walter randomly sorts volunteers into two groups of 25. He teaches the technique to the 25 subjects in one group. He does not teach the technique to the 25 subjects in the other group. After a week, all 50 subjects report how many headaches they had.
Number of headaches for people taught the stress management technique
  • 1
  • 2
  • 5
  • 2
  • 2
  • 4
  • 2
  • 1
  • 3
  • 2
  • 4
  • 3
  • 2
  • 3
  • 3
  • 1
  • 4
  • 0
  • 4
  • 3
  • 5
  • 2
  • 1
  • 0
  • 1
  • Mean:
     2.4
    headaches
Number of headaches for people not taught the stress management technique
  • 4
  • 4
  • 4
  • 4
  • 4
  • 1
  • 1
  • 1
  • 0
  • 5
  • 5
  • 4
  • 6
  • 3
  • 2
  • 1
  • 5
  • 1
  • 3
  • 2
  • 5
  • 4
  • 4
  • 5
  • 2
  • Mean:
     3.2
    headaches
How much lower is the average for the treatment group than the average for the control group?
headaches
ref_doc_title.

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