Having a good comparison group helps eliminate threats to internal validity by providing a basis for comparison and reducing confounding variables in research.
Selection bias affecting internal validity can occur due to missing data, differences in participation rates, or varying loss to follow-up between study groups, impacting the representativeness of the sample. Having a good comparison group helps mitigate threats to internal validity like selection bias, history threats, observer bias, and demand characteristics by providing a basis for comparison and reducing confounding variables. Maintaining comparable groups in research is essential for establishing a strong internal validity, ensuring that the observed effects are indeed due to the intervention.
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