A researcher ran a study to determine whether massage could help infertile women become pregnant. One

hundred and eighty healthy women undergoing treatment with artificial insemination participated in the

study. By drawing names from a hat, half of the subjects were randomly assigned to receive a massage

treatment 30 minutes before embryo transfer and again 30 minutes after the transfer. The remaining 90

subjects were instructed to lie still for 30 minutes after the embryo transfer. Results: In the massage group,

41 women became pregnant. In the control group, 25 women became pregnant. Explain how each of the

principles of experimental design (comparison, randomization, replication and control) was used in

this study.