Question

Does the herb St. John’s wort relieve major depression? Here is an excerpt from the report of one study of this issue: “Design: Randomized, Double-Blind, Placebo-Controlled Clinical Trial.” The study concluded that the difference in effectiveness of St. John’s wort and a placebo was not statistically significant.

a. Describe the placebo effect in this context. 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

Short answer

a. As, it gave some patients a pill that should have no effect at all but looks, tastes, and feels like the Saint-John’s-wort. These people think that they are being treated, but in fact, they are not. So if they get better, this would be a case of the placebo effect.

b. The purpose of this random assignment was to create two groups of subjects that are about the same in the beginning of the experiment. As this reduces bias in the conducting of the experiment.

c. Double-blind is when neither the patient or experimenter know what treatment is given. The subject should not know which treatment they are receiving so that the researchers can measure how much placebo effect there is. But the researchers should also be blinded so that they cannot influence how they measure the results.

d. “Not statistically significant” means in this context that the difference in improvement between the two groups was not large enough to rule out potential chance variation resulting for random assignment of the variables.

Step-by-step solution

Part a. Step 1. Explanation

As, it gave some patients a pill that should have no effect at all but looks, tastes, and feels like the Saint-John’s-wort. These people think that they are being treated, but in fact, they are not. So if they get better, this would be a case of the placebo effect.

Part b. Step 1. Explanation

The purpose of this random assignment was to create two groups of subjects that are about the same in the beginning of the experiment. As this reduces bias in the conducting of the experiment.

Part c. Step 1. Explanation

Double-blind is when neither the patient or experimenter know what treatment is given. The subject should not know which treatment they are receiving so that the researchers can measure how much placebo effect there is. But the researchers should also be blinded so that they cannot influence how they measure the results.

Part d. Step 1. Explanation

“Not statistically significant” means in this context that the difference in improvement between the two groups was not large enough to rule out potential chance variation resulting for random assignment of the variables.