Premature infants often have difficulty regulating their body temperature because of their low birth weight and low body fat. Researchers hypothesized that immersion bathing in warm water would improve temperature regulation relative to the common practice of sponge bathing. Eight infants were available to test the hypothesis; four were randomly assigned to each of the two conditions (immersion, sponge) during their stay in the neonatal intensive care unit (NICU). The dependent variable was body temperature 15 minutes after the bath. Contrary to the hypothesis, no difference in body temperature after the bath was found between the two groups.

A. A nurse noted that the two groups of infants were very different. The infants randomly assigned to the immersion condition weighed less and were born earlier, on average, than infants in the sponge condition. Explain how this difference between the two groups could have occurred despite the fact that random assignment to conditions was used, and how this difference might have impacted the results of the experiment.

B. The researchers decided to test the hypothesis again. This time, however, they considered the weight of the infants. Twelve infants were available for the study with the following weights (in pounds): 4.6, 5.0, 4.1, 4.0, 5.4, 5.8, 4.4, 4.9, 6.2, 5.2, 4.2, 4.6. Identify the research design you would recommend to conduct this study and explain how the infants should be assigned to the conditions of the experiment.

C. Suppose a social worker tested the bathing variable when she taught parenting skills during home visits. She reasoned that maintaining body temperature at home is more important than in the NICU, where incubators are used. She randomly assigned 20 parents of premature infants to learn to immerse their babies at the proper temperature, and 20 parents to be instructed about sponge bathing. The social worker also taught parents how to take the baby’s temperature 15 minutes after the bath (the dependent variable). Identify a goal of the social worker’s research that led her to focus on the setting for conducting her research. How would you describe the findings if both experiments showed that body temperature was higher for infants in the immersion condition relative to the spongebath condition?