What is a potential downside of applying overly strict inclusion and exclusion criteria in a study?

• A. They Limit Generalizability To Other Settings Or Populations
• B. They Maximize External Validity
• C. They Guarantee A Representative Sample
• D. They Significantly Increase External Validity

Answer: (A)

Overly strict inclusion and exclusion criteria create a highly selective study sample. That selectivity can help reduce confounding and improve the study’s internal validity, but it also narrows who the findings apply to. When the sample doesn’t resemble the broader population or other settings, the results don’t generalize well—generalizability to other settings or populations is limited. So the main downside is reduced applicability beyond the studied group.

The other statements propose that strict criteria maximize external validity, guarantee a representative sample, or greatly increase external validity. In reality, they do the opposite: such criteria typically limit generalizability and don’t guarantee representativeness, so external validity is not enhanced.