Chapter 11, Problem 21E

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.

21. Over a 4-month period, among 30 people with bipolar disorder, patients who were given a high dose (10 g/day) of omega-3 fats from fish oil improved more than those given a placebo. (Archives of General Psychiatry 56 [1999]: 407)