liveBook · Manning

Ignorability

As explained in Causal Inference for Data Science

The ignorability assumption, also called exchangeability, is the condition that potential outcomes are independent of treatment assignment conditional on specified covariates.

Ignorability, also called exchangeability, allows adjustment for covariates when potential outcomes are independent of treatment assignment conditional on those covariates. Under this assumption, the adjustment formula can estimate the average treatment effect without bias. In an RCT, random assignment makes treatment groups comparable in characteristics such as age, socioeconomic class, and sex. section 10.3

Keep these distinctions in view:

  • The assumption appears under several names, including strong ignorability and exchangeability; some treatments also include positivity under this label. section 10.3
  • In the potential-outcomes framework, ignorability provides the condition for applying the adjustment formula; DAGs instead use the back-door criterion to identify suitable adjustment sets. section 10.3 section 10.6

Comparing treatment groups

Suppose an RCT assigns patients to treatment or control. For any age a, randomization implies approximately equal probabilities of observing that age in both groups: P(Age = a | T = 1) = P(Age = a | T = 0). This balance illustrates why treatment assignment can be treated as independent of measured patient characteristics. section 10.3

How Causal Inference for Data Science covers it

How deep it goes
Defines conditional independence, motivates it through randomization, and connects it to adjustment for the average treatment effect.
Examples
Uses randomized treatment assignment and equal age proportions across treated and untreated patients.
What it assumes
Introduces the assumption step by step while assuming familiarity with treatment assignment and potential outcomes.
What you can do after
Apply the adjustment formula when covariates satisfy the ignorability assumption.
How it connects
Links potential outcomes, exchangeability, adjustment formulas, DAGs, the back-door criterion, and positivity.

Also explained in

Compare how 2 books explain ignorability →

Related concepts

This explainer was generated by Manning's knowledge graph from the text of Causal Inference for Data Science. The section links point to the parts of the book it draws on.