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Directed Acyclic Graphs
“An arrow diagram forces the causal story into the open before the statistical model is touched.”
01 / SUMMARY
In short
A DAG represents variables as nodes and assumed causal relations as arrows without directed cycles. It supports reasoning about open paths, adjustment, and assumptions that data alone do not establish.
03 / SCENE
In the wild
Drawing age → activity and age → health makes the confounding path between activity and health visible.
04 / LIMIT
The limit
The diagram does not automatically discover causal truth; it formalizes knowledge and assumptions that may be wrong.
FINAL NOTE
What remains
Expose the debatable arrows before choosing controls.