Which sampling method is most likely to produce external validity issues due to limited diversity?

• A. Stratified Sampling
• B. Simple Random Sampling
• C. Convenience Sampling
• D. Systematic Sampling

Answer: (C)

External validity is about how well findings generalize to a broader population, setting, or time. The sampling method shapes how diverse the sample is. Convenience sampling, where participants are chosen because they’re easiest to recruit, tends to come from a narrow group—such as students from a single class, volunteers from one location, or people nearby. This creates limited diversity and overrepresents certain characteristics while missing others, so the results may not apply to people outside that readily reachable group. For example, studying attitudes toward a health policy by surveying only college students in one city would likely not reflect the views of older adults or people from different regions. In contrast, stratified sampling ensures representation across important subgroups, simple random sampling gives everyone in the population an equal chance, and systematic sampling selects participants at regular intervals along a list; these approaches can enhance diversity and generalizability when done properly. Therefore, convenience sampling is most likely to introduce external validity issues due to restricted diversity.