Simpson's Law

Simpson's Law states that the overall characteristics of a combined population can differ from those of its individual groups due to the way data is aggregated. This phenomenon occurs when subgroup proportions vary across different categories, leading to misleading conclusions if not properly analyzed. For example, a treatment might seem effective overall, but when you look at specific subgroups, it could be less effective or harmful. It highlights the importance of examining data both at the group level and the aggregate level to avoid incorrect assumptions based on aggregated statistics alone.