Among a group of disabled women aged 65 and older who were tracked for several years, those who had a vitamin B12 deficiency were twice as likely to suffer severe depression as those who did not.
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.