A Causal Calculus for Statistical Research

  • Judea Pearl
Part of the Lecture Notes in Statistics book series (LNS, volume 112)


A calculus is proposed that admits two conditioning operators: ordinary Bayes conditioning, P (y|X = x), and causal conditioning, P (y|set(X = x)), that is, conditioning P (y) on holding X constant (at x) by external intervention. This distinction, which will be supported by three rules of inference, will permit us to derive probability expressions for the combined effect of observations and interventions. The resulting calculus yields simple solutions to a number of interesting problems in causal inference and should allow rank-and-file researchers to tackle practical problems that are generally considered too hard, or impossible. Examples are:
  1. 1.

    Deciding whether the information available in a given observational study is sufficient for obtaining consistent estimates of causal effects.

  2. 2.

    Deriving algebraic expressions for causal effect estimands.

  3. 3.

    Selecting measurements that would render randomized experiments unnecessary.

  4. 4.

    Selecting a set of indirect (randomized) experiments to replace direct experiments that are either infeasible or too expensive.

  5. 5.

    Predicting (or bounding) the efficacy of treatments from randomized trials with imperfect compliance.

Starting with nonparametric specification of structural equations, the paper establishes the semantics necessary for a theory of interventions, presents the three rules of inference, and proposes an operational definition of structural equations.


Causal Effect Causal Theory Manipulate Variable Causal Information Causal Diagram 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.


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Copyright information

© Springer-Verlag New York, Inc. 1996

Authors and Affiliations

  • Judea Pearl
    • 1
  1. 1.Cognitive Systems Laboratory Computer Science DepartmentUniversity of California, Los AngelesLos AngelesUSA

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