Students in a developmental psychology lab course conducted an observational study of parent–infant interactions in the home. When they first entered the home on each of the 4 days they observed a given family, they greeted both the parents and the infant (and any other children at home). They instructed the family to follow its daily routine, and they asked a series of questions about the activities of that day to determine whether it was a “normal” day or whether anything unusual had happened. The students tried to make the family feel comfortable, but they also tried to minimize their interactions with the family and with each other. For any given 2-hour observation period there were always two student observers present in the home, and the two observers recorded their notes independently of each other. Each of six pairs of students was randomly assigned to observe two of the 12 families who volunteered to serve in the study. The same pair of observers always observed a given family for the entire 8 hours of observation for that family. The observers used rating scales with clearly defined labels to record behaviors on a number of different dimensions, such as mutual warmth and affection of the parent–infant interaction.

A. Cite two specific procedures used by the students to ensure the reliability of their findings.

B. Cite one possible threat to the external validity of the findings of this study; once again, cite a specific example from the description provided.

C. Cite one specific aspect of their procedure that indicated that the students were sensitive to the possibility that their measurements might be reactive. What other methods might they have used to deal with this problem of reactivity?