What is the difference between internal and external validity in causal inference?
Instruction: Define both concepts and explain their importance in the context of causal inference.
Context: This question tests the candidate's knowledge of the key concepts of internal and external validity and their implications for the generalizability and applicability of study findings.
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Internal validity concerns whether the study supports its stated causal comparison for its study population and conditions. Threats include confounding, differential missing outcomes, measurement changes, nonadherence and interference. Randomization supports the assignment comparison, but does not guarantee exact finite-sample balance or fix all implementation problems.
External validity concerns whether that effect applies to a specified...