Chapter 4, Problem R4.8RE

(a)

To determine

To describe the placebo effect in this context and how did the design of this experiment account for the placebo effect.

Explanation of Solution

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)

To determine

To explain the purpose of the random assignment.

Explanation of Solution

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)

To determine

To explain why is a double blind design a good idea in this setting.

Explanation of Solution

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)

To determine

To explain what “not statistically significant” means in this context.

Explanation of Solution

“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.