Question: An herb for depression? Does the herb SaintJohn's-wort relieve major depression? Here is an excerpt from the report of a study of this issue: "Design: Randomized, Double-Blind, PlaceboControlled Clinical Trial." The study concluded that the difference in effectiveness of Saint-John'swort and a placebo was not statistically significant.
(a) How did the design of this experiment account for the placebo effect?
(b) Explain the purpose of the random assignment.
(c) Why is a double-blind design a good idea in this setting?
(d) Explain what "not statistically significant" means in this context.