Strategies of Research Design with Confounding: A Graphical Description

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Research design is of paramount importance when attempting to overcome con- founding. In this paper, we propose a unified graphical approach for the consideration of cross-sectional research designs. Specifically, we argue that at least five distinct strategies may be discerned for coping with the presence of a common-cause con- founder: (1) blocking backdoor paths, (2) mechanisms, (3) instrumental variables, (4) alternate outcomes, and (5) causal heterogeneity. All of these strategies enlist a facil- itating variable, whose role defines the corresponding research design. This resulting framework builds on the foundational work of Pearl (2000, 2009) but incorporates addi- tional research designs into the graphical framework, providing a more comprehensive typology of designs for causal inference.

Last updated on 07/05/2013