An investigator studied the effects of three different antidepressants (A, B, and C) on patient ratings of depression. To do this, patients were stratified into six age– gender combinations. From a random sample of three patients from each stratum, the experimenter randomly allocated the three antidepressants. On the day the study was to be initiated, a baseline (pretreatment) depression scale rating was obtained from each patient. The assigned therapy was then administered and maintained for 1 week. At that time, a second rating (posttreatment) was obtained from each patient. The pre- and posttreatment ratings appear next (a higher score indicates more depression).
a. Identify the experimental design.
b. Write a first- order model relating the posttreatment response y to the pretreat-ment rating x1 for each treatment.

  • CreatedNovember 21, 2015
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