An introduction to g methods

Int J Epidemiol. 2017 Apr 1;46(2):756-762. doi: 10.1093/ije/dyw323.


Robins' generalized methods (g methods) provide consistent estimates of contrasts (e.g. differences, ratios) of potential outcomes under a less restrictive set of identification conditions than do standard regression methods (e.g. linear, logistic, Cox regression). Uptake of g methods by epidemiologists has been hampered by limitations in understanding both conceptual and technical details. We present a simple worked example that illustrates basic concepts, while minimizing technical complications.

Keywords: G Estimation; G Formula; G Methods; Inverse Probability Weighting; Marginal Structural Model; Monte Carlo Estimation; Structural Nested Model.

MeSH terms

  • Causality*
  • Computer Simulation
  • Confounding Factors, Epidemiologic
  • Epidemiologic Research Design*
  • Humans
  • Models, Statistical*