Which sampling method primarily enhances external validity?

Which sampling method primarily enhances external validity?

• A. Random Selection
• B. Random Assignment
• C. Convenience sampling
• D. Stratified sampling

Answer: (A)

External validity is about how well the study’s findings generalize to the broader population. The method that best boosts this generalizability is random selection, because when every member of the target population has an equal chance of being included, the sample is more likely to reflect the population’s overall diversity. This reduces selection bias and makes observed effects more likely to occur in the real world, not just in the study group. Random assignment, on the other hand, helps ensure internal validity by making groups comparable within the study, but it doesn’t by itself guarantee that the sample represents the population. Convenience sampling tends to produce a biased, non-representative group, which limits generalizability. Stratified sampling can improve representation of important subgroups, which can be useful in certain contexts, but the strongest route to broad external validity is truly random selection of participants.

External validity is about how well the study’s findings generalize to the broader population. The method that best boosts this generalizability is random selection, because when every member of the target population has an equal chance of being included, the sample is more likely to reflect the population’s overall diversity. This reduces selection bias and makes observed effects more likely to occur in the real world, not just in the study group.

Random assignment, on the other hand, helps ensure internal validity by making groups comparable within the study, but it doesn’t by itself guarantee that the sample represents the population. Convenience sampling tends to produce a biased, non-representative group, which limits generalizability. Stratified sampling can improve representation of important subgroups, which can be useful in certain contexts, but the strongest route to broad external validity is truly random selection of participants.