What is the threats to the internal validity of Cross-sectional design?

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What is the threats to the internal validity of Cross-sectional design?



Answer: The groups of subjects in a cross-sectional study are currently different ages, so they must have been born at different times. This means that they are members of different cohorts and, so, maybe any difference in their behavior right now is due to a difference between cohorts, instead of a difference due to current age.

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