Selection and collider pathway audit ==================================== StatMedAnalysis | Original downloadable worksheet | 6 November 2026 Identify selection rules that can open misleading exposure–outcome associations. How to use this worksheet Write every rule that determines inclusion in the analysis sample. For each rule, list factors that cause selection. Check whether exposure and causes of the outcome can both affect selection. Compare the target population with the selected sample and document the implications before adjustment. Save a working copy and keep the original blank version. Use public, hypothetical or aggregate information only; do not enter patient identifiers, credentials or confidential records. Keep source evidence in your approved project workspace. Mark unresolved text fields UNKNOWN or NOT REPORTED with a reason; never substitute zero for an unknown count. Project/version __________________ Prepared by role/date __________________ Working fields 1. Target population Response/evidence: _________________________________________________________ ___________________________________________________________________________ 2. Selection or restriction variable Response/evidence: _________________________________________________________ ___________________________________________________________________________ 3. Causes of selection Response/evidence: _________________________________________________________ ___________________________________________________________________________ 4. Exposure-to-selection pathway Response/evidence: _________________________________________________________ ___________________________________________________________________________ 5. Outcome-cause-to-selection pathway Response/evidence: _________________________________________________________ ___________________________________________________________________________ 6. Conditioning performed by design or model Response/evidence: _________________________________________________________ ___________________________________________________________________________ 7. Potential induced association Response/evidence: _________________________________________________________ ___________________________________________________________________________ 8. Alternative sampling or analysis strategy Response/evidence: _________________________________________________________ ___________________________________________________________________________ Hypothetical worked case A fictional hospital-only sample includes people whose admission depends on both an exposure and unrelated disease severity. Restricting to admitted patients may create an association between those causes even if none exists in the source population. Decision rule and limitations Flag conditioning on a common effect for causal review. Removing a variable from a regression does not undo selection already imposed by sample construction. Decision _______________________ Remaining uncertainty ____________________ Next action ____________________ Owner / review date ______________________ Independent check and discrepancy resolution _______________________________ Official method or reporting reference checked 6 November 2026 https://miguelhernan.org/whatifbook This is an original planning aid, not an official checklist, validated instrument, clinical recommendation or certificate of expert approval. Apply the referenced guidance to the specific design and record any additional requirements.