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Causal Confounding
“Two groups may differ before the supposed treatment in a way that also changes the outcome.”
01 / SUMMARY
In short
Confounding occurs when a common cause, or equivalent structure, mixes the exposure's effect with baseline differences. Adjustment can help only when the needed variables are properly identified and measured.
03 / SCENE
In the wild
People taking a supplement also exercise more; comparing health without handling exercise mixes the two processes.
04 / LIMIT
The limit
Adding every available variable to a regression can create bias when one is a mediator or collider.
FINAL NOTE
What remains
Choose adjustments from a causal model, not an automatic covariate list.