1. Saint-John's-wort and depression. Does the herb Saint-John's-wort relieve major depression? Here are some excerpts from the report of a study of this issue.24 The study concluded that the herb is no more effective than a placebo.
(a) "Design: Randomized, double-blind, placebo- controlled clinical trial." Explain the meaning of each of the terms in this description.
(b) "Participants ...were randomly assigned to receive either Saint-John's-wort extract (n = 98) or placebo (n = 102).... The primary outcome measure was the rate of change in the Hamilton
Rating Scale for Depression over the treatment period." Based on this information, use a diagram to outline the design of this clinical trial.
2. speed delivery yet more? What about mailing a letter on Monday, Thursday, or Saturday? Describe the design of an experiment on the speed of ?rst-class mail delivery. For simplicity, suppose that all letters go from you to a friend, so that the sending and receiving locations are ?xed.