What the worksheet covers
Four blocks, one problem. The How to use tab explains the method, where it comes from, its limits, and the common failure modes: stopping at 'operator error', restating instead of explaining, chains built on opinion. The 5-Whys Worksheet tab walks the problem through a facts-only statement, a why chain with an evidence reference on every row, a recurrence test before the root cause is accepted, and corrective action rows with owner, due date, status, and effectiveness criteria. The Worked Example tab shows a completed chain from a generic packaging line, so the standard of evidence expected on each row is visible rather than described.
- Problem statement block — what, where, when, and how big; observed facts only
- Five why rows, each with an evidence reference column
- A recurrence test before the root cause is accepted
- Corrective action rows with a named owner, a due date, and a status
- Effectiveness criteria defined at approval time, not at review time
When 5-Whys works — and when it does not
The 5-Whys technique comes from the Toyota Production System and the wider lean manufacturing tradition: keep asking why until the answer is a cause in the process, not in a person. Five is a guideline, not a rule — the chain is finished when it reaches a cause that, if corrected, prevents recurrence, whether that takes three whys or seven.
The honest limit: 5-Whys suits problems with a single dominant causal chain. When an answer has more than one credible 'because', forcing a single chain produces a confident wrong answer — the worksheet's instruction for that case is to branch the chain or switch to a multi-factor tool such as a fishbone (Ishikawa) diagram or a fault tree, and to record that decision as part of the analysis.
Where this fits in a CAPA process
This is the method sheet for the root-cause step itself — it is deliberately narrower than our deviation investigation checklist, which structures the whole investigation from intake to closure, and it hands off to the CAPA effectiveness check, which picks up after actions are taken. Used together: the checklist tells you what to document, this worksheet disciplines how the cause is found, and the effectiveness check verifies the fix held.
Quality system standards and regulations require investigating the cause of nonconformities — ISO 13485:2016 clause 8.5.2 (corrective action) and the FDA CAPA requirement historically stated in 21 CFR 820.100, carried forward under the QMSR through its incorporation of ISO 13485; ICH Q10 likewise expects a CAPA system within a pharmaceutical quality system. None of them mandates a specific root cause method. What they expect is a documented, evidence-based analysis — which is exactly the discipline this worksheet enforces. An inspector reading the worksheet will go to the last why and ask why you stopped; if the answer is a person, the chain is not finished.
