Chapter 4.3, Problem 101E

(a)

To determine

To explain why did the researcher randomly assign the subjects to the two treatments.

Explanation of Solution

The subjects were randomly assigned to the treatments to make sure that the treatment groups are as similar as possible. This is necessary to be sure that the results of the treatment are due to treatment itself and not due to significantly different groups of subjects. Thus also to make sure that the two treatments groups are as similar as possible.

(b)

To determine

To explain what does the statement given means.

Explanation of Solution

The difference in the percent of women who became pregnant in the two groups is statistically significant means that the difference in result were so extreme that the difference cannot be caused by chance. Also the study is deemed statistically significant if there's a very low probability the result could have occurred by chance.

(c)

To determine

To explain why the design of the study prevent us from concluding that the acupuncture caused the difference in pregnancy rates.

Explanation of Solution

The design of the study prevent us from concluding that the 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 treatment to give accurate results.