Anaes Vivas · Measurement & monitoring physics

Data viva — the confounder triangle and the funnel plot

A data viva on the two diagrams at the heart of bias and confounding. The confounder triangle: a confounder is associated with both exposure and outcome but not on the causal pathway, so it manufactures an apparent association that disappears once controlled; the boundary with a mediator. The funnel plot: symmetry means no publication bias; asymmetry (missing small negative studies) signals publication bias. Defences — randomisation as the only control for unknown confounders; trial registration and CONSORT against publication bias.