Collider

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Back to Causal Thinking

Types of junctions

A three-node network with two links is called a junction. These are the building blocks of all Bayesian- and causal networks. There are three basic types of junctions, with the help of which we can characterise any pattern of arrows in a three node network.

  • A → B → C (see mediator or chain)
  • A ← B → C (see confounder or fork)
  • A → B ← C (collider)

Collider

A → B ← C

The collider pattern works in precisely the opposite way from chains or forks. If A and C are independent, to begin with, their relationship with B will make them dependent.

Let us consider: A = entrepreneurship, C =  capital and B = success.

Entrepreneurship and capital contribute to business success. This is the positive story: success depends on entrepreneurship and capital. We also know the collider bias or the “explain-away” effect. If A is an excellent entrepreneur and has success, that “explains away” his need to have more capital than the average person. (1)

Source
(1) The Book of Why - J. Pearl & D. Mackenzie - Basic Books - 2018

Examples from the field

  • Operational Strategy → Requisite organisation ← Financial management
    • The (new) operational strategy requires some (new) functions in the organisation but budget cuts prevent this. Both departments (Operational Strategy and Financial management) refer to the organisation to fix the problem.
  • Operational Strategy → Business model ← Commercial management
    • Operational Strategy imposes new directives on the Business model (from Long term thinking) while Commercial management driven by the current market situation leave everything as it is.