External Validity

External validity refers to the extent to which research findings from one study generalize to or across groups of people, settings, treatments, and time periods. In other words, to what extent does the size or direction of a researched relationship remain stable in other contexts and among different samples? In an effort to measure precise effect sizes and control for confounding variables, many scholars use survey methods featuring hypothetical or retrospective reports, whereas others examine communication phenomena in sterile research labs. In addition, the findings of many social scientific studies are based on the responses of convenience samples consisting of college students and volunteers. While these studies contribute to the growing body of communication scholarship, concerns about their results’ applicability to broader, more diverse populations of people in real-life contexts remain.

In recent years, scholars, practitioners, and editors have expressed a renewed commitment to conducting and supporting rigorous research with high levels of external validity. For example, researchers who examine the effectiveness of communication skills training programs or health interventions want to ensure that the findings of their studies are generalizable to target populations beyond their specific research studies’ samples. Similarly, communication scientists who study message effects aim to produce replicable, generalizable findings that would ring true outside of laboratories and simulated survey scenarios, and researchers seeking external funding must assure grant program officers and foundations that the results of their pilot data are not limited to their immediate research participants. Recognizing the importance of external validity, researchers are attending to the ways they design their studies, collect data, and report their findings. This entry focuses on four central issues to external validity: sampling, ecological validity, replication, and reporting. Each of these issues is explored in this entry.