Chapter 11, Problem 28E

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.

28. Scientists at a major pharmaceutical firm investigated the effectiveness of an herbal compound to treat the common cold. They exposed each subject to a cold virus, then gave him or her either the herbal compound or a sugar solution known to have no effect on colds. Several days later, they assessed the patient’s condition, using a cold severity scale ranging from 0 to 5. They found no evidence of benefits associated with the compound.