Explain 'Simpson's Paradox'.

Explain 'Simpson's Paradox'.

Approach: Describe how a trend appears in groups but reverses when combined.

A phenomenon in which a trend appears in several different groups of data but disappears or reverses when these groups are combined. It usually occurs when there is a lurking confounding variable.

Follow-up: Give a classic example (e.g., UC Berkeley admissions).

Key concepts: confounding variables, aggregation.