Dr. Guidry conducts a study examining the relationship between the number of friends one has and the experience of daily stress and life satisfaction. She randomly samples 1,500 elderly men and women in Nashville, Tennessee (the state capital), located in the southern United States. Below are her findings. • Life satisfaction and experience of daily stress: r = −.57 (p = .01) • Number of friends one has and experience of daily stress: r = .09, not sig. • Number of friends one has and life satisfaction: r = .36 (p = .04) Dr. Guidry submits her study for publication in a scientific journal. If one of the peer reviewers is concerned about the external validity of her study, which of the following is the most important aspect of Dr. Guidry’s study to consider?

a. Outliers
b. Moderators
c. Random
d. Curvilinear scores

In this study, Dr. Guidry reaches a particular conclusion based on her research. If the numbers were collected and calculated correctly, and the study was rigorously done, then the study most likely has internal validity. However, in order for it to also have external validity, the results of the study should accurately reflect the population. Therefore, in order for this to be the case, we need to be sure that the sample drawn was indeed random.