Past exam of the mathematics course of the University of Cambridge / 2025 / iii / Paper 207 / 1 / e / ii / Solution

External validity is weaker because affluent, healthy volunteers need not have the same baseline risk or sugar effect as the UK target population. Generalization requires either negligible effect modification by selection-related characteristics or standardization and inverse-probability weighting to the target population using variables measured in both sources. The unweighted estimate should otherwise be described as an effect for Biobank-like participants.