Davila was interested in finding out how people would sleep after being told that the house they were in was infested with spiders. She randomly selected 28 people from her school to participate in the study. She randomly assigned 14 of the people to sleep in the house on Friday night, when she told them all that it was infested. The other 14 slept in the house on Saturday night and were not told that the house was infested. She then measured how long each person slept and found that those in the “infested” group got fewer hours of sleep than those in the “not-infested” group. A confound in this study is
A Whether or not they were told that the house was infested.
B The amount of sleep they got.
C The night they slept at the house.
D The class that they were chosen from.
The correct answer and explanation is:
The correct answer is C. The night they slept at the house.
A confound is an extraneous factor that influences both the independent and dependent variables, making it difficult to determine the cause of the observed effect. In this study, the independent variable is whether participants were told that the house was infested with spiders, and the dependent variable is the amount of sleep the participants got.
However, a confounding factor arises from the fact that participants in the “infested” group slept on Friday night, while participants in the “not-infested” group slept on Saturday night. This introduces a potential bias because the two groups were exposed to different conditions beyond the infested status of the house. For instance, people may sleep differently on Friday night versus Saturday night due to factors such as:
- End of the workweek fatigue: Participants who slept on Friday night may have been more tired from the week, influencing their sleep duration.
- Environmental differences: There could have been differences in noise, temperature, or other environmental factors between Friday and Saturday that affected sleep quality and quantity.
Therefore, the night participants slept at the house (Friday vs. Saturday) is a confound because it could have influenced the amount of sleep they got, making it difficult to attribute differences in sleep solely to the perception of the house being infested.
To eliminate this confound, Davila could have had all participants sleep on the same night or counterbalanced the nights so that both groups slept on both nights, reducing the potential for the night to influence the results.