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Generalizability: the trees, the forest, and the low-hanging fruit
Walter A Kukull1, Mary Ganguli
1Department of Epidemiology, University of Washington School of Public Health, Seattle, USA. kukull@u.washington.edu
Neurology
|June 6, 2012
Summary
This study clarifies sample representativeness and result generalizability in research. It distinguishes internal and external validity, identifying bias and confounding threats in study design.
Area of Science:
- Epidemiology
- Clinical Research Methodology
Background:
- Increasing focus on study sample representativeness and result generalizability in clinical and epidemiologic research.
- Common misconstruction and conflation of these concepts with internal and external validity.
Purpose of the Study:
- Define and differentiate internal and external validity.
- Explain the relationship between validity and generalizability.
- Identify threats to validity and practical design issues.
Main Methods:
- Conceptual clarification of validity and generalizability.
- Illustrative examples of bias and confounding.
- Discussion of practical study design elements.
Main Results:
- Distinction between internal validity (bias, confounding) and external validity (generalizability).
- Identification of specific threats to validity in study design.
- Practical considerations for sample selection and exposure assessment.
Conclusions:
- Clear definitions and relationships between validity and generalizability are crucial.
- Understanding threats to validity improves research rigor.
- Practical guidance for designing representative and generalizable studies.
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