What does transportability refer to in cohort studies?

• A. Ability to apply findings to other populations or settings
• B. Internal validity only
• C. Statistical power
• D. The speed of data collection

Answer: (A)

Transportability refers to whether the findings from a cohort study can be applied to populations or settings beyond the one studied. This is about external validity or generalizability—can the observed association hold in a different group with different characteristics or in a different context? It’s not about internal validity, which deals with biases within the study itself, nor about statistical power, which concerns the ability to detect an effect given the sample size, nor about how quickly data were collected. In practice, transportability considers whether differences in age, risk factors, or context might change the effect, and it often involves clearly describing the study population and setting and, when possible, validating findings in other groups or using methods that estimate what would happen in a target population.