Negative-control rationale worksheet ==================================== StatMedAnalysis | Original downloadable worksheet | 6 November 2026 Document what a negative-control result can and cannot reveal about bias. How to use this worksheet Choose a control exposure or outcome based on a defensible absence of the target causal pathway. Explain which confounding or measurement mechanisms the control shares with the main analysis. Prespecify how each possible result will be interpreted and whether it changes further sensitivity analysis. 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. Main causal question Response/evidence: _________________________________________________________ ___________________________________________________________________________ 2. Control exposure or outcome Response/evidence: _________________________________________________________ ___________________________________________________________________________ 3. Why target causal effect should be absent Response/evidence: _________________________________________________________ ___________________________________________________________________________ 4. Shared bias pathway Response/evidence: _________________________________________________________ ___________________________________________________________________________ 5. Important nonshared mechanisms Response/evidence: _________________________________________________________ ___________________________________________________________________________ 6. Planned analysis and precision Response/evidence: _________________________________________________________ ___________________________________________________________________________ 7. Interpretation of nonnull result Response/evidence: _________________________________________________________ ___________________________________________________________________________ 8. Interpretation of null result Response/evidence: _________________________________________________________ ___________________________________________________________________________ Hypothetical worked case A fictional control outcome is measured through the same clinic system but should not be caused by the exposure. An association could indicate confounding or detection bias; a null result with a wide interval would not certify an unbiased main estimate. Decision rule and limitations Reject a control with a plausible target causal pathway or materially different ascertainment. Treat control analyses as bias probes whose interpretation depends on assumptions, not pass/fail certificates. 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.