Chapter 4.2, Problem 73E

(a)

To determine

To describe how the three principles of experimental design were addressed in this study.

Explanation of Solution

In the question, a study sought to determine whether the ancient Chinese art of acupuncture would help infertile women becomes pregnant. Thus, the three principles of experimental design are as:

Control effects of lurking variables and use at least two groups to compare, Randomly assign subjects to each group and Replication.

Thus, the usage of these in the study is as:

There are two groups: One group received acupuncture, while the other group did not receive acupuncture. Thus, control lurking variables are as: One group received acupuncture, while the other group did not receive acupuncture and was asked to lie still equally long. And subjects were randomly assigned to a treatment group. So, the experiment contains $160$ subjects.

(b)

To determine

To explain what this means to someone who knows little statistics.

Explanation of Solution

In the question, a study sought to determine whether the ancient Chinese art of acupuncture would help infertile women becomes pregnant. And it is given that the difference in the percent of women who became pregnant in the two groups is statistically significant. Thus, the statistically significant difference means that the difference in results were so extreme that the difference cannot be caused by chance.

(c)

To determine

To explain why placebo effect prevent us from concluding that acupuncture caused the difference in pregnancy rates.

Explanation of Solution

In the question, a study sought to determine whether the ancient Chinese art of acupuncture would help infertile women becomes pregnant. Thus, the placebo effect prevent us from concluding that acupuncture caused the difference in pregnancy rates because the women who did not receive acupuncture were aware of this fact and thus we have not been able to take into account the placebo effect of receiving acupuncture. To take into account this placebo effect there should be a third group that receives a fake acupuncture treatement.