An herb for depression? Does the herb Saint-

John’s-wort relieve major depression? Here is an excerpt from the report of a study of this issue:

“Design: Randomized, Double-

Blind, Placebo-

Controlled Clinical Trial.”63 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.