Chapter 11, Problem 24E

21–34. What’s the design? Read each brief report of statistical research, and identify

  a) whether it was an observational study or an experiment.

If it was an observational study, identify (if possible)

  b) whether it was retrospective or prospective.

  c) the subjects studied and how they were selected.

  d) the parameter of interest.

  e) the nature and scope of the conclusion the study can reach.

If it was an experiment, identify (if possible)

  b) the subjects studied.

  c) the factor(s) in the experiment and the number of levels for each.

  d) the number of treatments.

  e) the response variable measured.

  f) the design (completely randomized, blocked, or matched).

  g) whether it was blind (or double-blind).

  h) the nature and scope of the conclusion the experiment can reach.

24. Is diet or exercise effective in combating insomnia? Some believe that cutting out desserts can help alleviate the problem, while others recommend exercise. Forty volunteers suffering from insomnia agreed to participate in a month-long test. Half were randomly assigned to a special no-desserts diet; the others continued desserts as usual. Half of the people in each of these groups were randomly assigned to an exercise program, while the others did not exercise. Those who ate no desserts and engaged in exercise showed the most improvement.