Determine whether an observational study or an experimental study is used. Two groups of infants were randomly selected. The infants in Group 1 were born prematurely, and the infants in Group 2 were born at full term. At the end of six months, the average height and weight for each group were compared. Experimental observational

This study is observational because the researchers are merely observing and comparing the outcomes (height and weight) of two naturally occurring groups of infants without interfering or manipulating any variables. They did not randomly assign infants to groups; rather, they used existing conditions (prematurity vs. full-term birth) as their groups. While the infants were randomly selected for inclusion in the study, that does not make it an experimental study. In experiments, researchers actively intervene or manipulate conditions, which is not the case here—this is all about measuring and comparing the outcomes of groups based on their inherent characteristics.