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  "path": "/t/collider-in-rct-subgroup-analysis/28689?page=2#post_36",
  "publishedAt": "2026-06-07T10:55:29.000Z",
  "site": "https://discourse.datamethods.org",
  "textContent": "Your analysis, thinking mechanistically about subgroup gates, makes it difficult for your reader to justify treating enrollment gates as if they were merely administrative criteria. They too become biological claims about what causal system is being randomized.\n\nAt both the enrollment gate and the subgroup gate, the central question is the relationship of the gating variable to the underlying causal pathway. For subgroups this appears as the prognostic-versus-predictive distinction. For enrollment criteria it appears as the mechanism-defining-versus-severity-defining distinction. These are closely related manifestations of the same causal problem.\n\nElias_Eythorsson:\n\n> You have written a paper that shows problems with this framework if the subgroup is defined by a pos-randomization variable but most of us were considering pre-randomization\n\nI agree that the statistical concerns differ between post-randomization and pre-randomization gates. The point is not that they generate the same bias. Rather, Doi’s mechanistic framework forces us to ask what biological role the gating variable plays. Once that question is asked for subgroup gates, it becomes difficult to avoid asking the same question of enrollment gates. The issue is no longer randomization integrity but causal-system integrity. Both involve interpreting a gate in relation to the underlying biological pathway, even though they occur at different points in the trial.",
  "title": "Collider in RCT Subgroup Analysis"
}