From sample average treatment effect to population average treatment effect on the treated: combining experimental with observational studies to estimate population treatment effects

• Published in: Journal of the Royal Statistical Society. Series A, Statistics in society Vol. 178; no. 3; pp. 757 - 778
• Main Authors: Hartman, Erin, Grieve, Richard, Ramsahai, Roland, Sekhon, Jasjeet S.
• Format: Journal Article
• Language: English
• Published: Oxford Blackwell Publishing Ltd 01.06.2015; John Wiley & Sons Ltd; Oxford University Press
• Subjects: Average; Causal inference; Clinical trials; Cost effectiveness analysis; Cost efficiency; Cost-effectiveness; Cost-effectiveness studies; Entropy; Estimation; Estimation bias; External validity; Intubation; Medical treatment; Observational studies; Placebo tests; Placebos; Political action committees; Population; Population distributions; Population estimates; Pulmonary arteries; Pulmonary artery catheterization; Randomized controlled trials; Sample surveys; Side effects; Statistics
• ISSN: 0964-1998; 1467-985X
• DOI: 10.1111/rssa.12094

Randomized controlled trials (RCTs) can provide unbiased estimates of sample average treatment effects. However, a common concern is that RCTs may fail to provide unbiased estimates of population average treatment effects. We derive the assumptions that are required to identify population average treatment effects from RCTs. We provide placebo tests, which formally follow from the identifying assumptions and can assess whether they hold. We offer new research designs for estimating population effects that use non-randomized studies to adjust the RCT data. This approach is considered in a cost-effectiveness analysis of a clinical intervention: pulmonary artery catheterization.