FILE SELECTED // FILE 00
Collider Bias
“Filtering on a shared consequence can manufacture a relationship between its causes.”
01 / SUMMARY
In short
A collider receives arrows from two variables. Conditioning, adjusting, or selecting on it can open a previously closed path and create a spurious association.
03 / SCENE
In the wild
Talent and connections affect admission to a selective school; among admits, conditioning on admission can make them look inversely related.
04 / LIMIT
The limit
Not every third variable should be controlled; some must remain unadjusted to avoid opening bias.
FINAL NOTE
What remains
Before filtering, ask whether the variable is a consequence of two relevant processes.