5 Whys template for 8D D4: occurrence, escape and verification

Most 5 Whys sheets that reach a customer are one column of answers. The reviewer has to take every “why” on trust, and the escape question is often missing. This template fixes both: it splits the analysis into an occurrence chain and an escape chain, and it puts the evidence next to each answer. It is the worksheet and how to fill it in. For choosing between tools, see fishbone vs 5 Whys in D4; for what D4 must contain overall, see how to write a D4 root cause.

What the template contains

• Header: complaint or 8D number, part, the D2 problem statement with numbers, and the starting fact.
• Chain A, occurrence: why the defect was made, down to a process, method, tool or system cause.
• Chain B, escape: why the existing controls didn’t detect it, starting from the check that should have caught it.
• Four columns per chain: why number, answer (a fact), evidence or how it was verified, and status (confirmed, ruled out or open).
• Verification box: each root cause, its check and the result.
• Hand-over to D5: one permanent action per verified cause.

How to fill it in

1. Start from a verified fact. Copy the problem statement from D2 and write the first fact you have confirmed: the station, tool, lot or shift. Don’t start from a theory.
2. Ask why, and write only what you can check. Each answer should be something a record, a measurement or a test can confirm or rule out.
3. Fill the evidence column as you go. If an answer has no evidence yet, mark it “open” and write the test you will run and the date. Don’t build the next why on an open answer.
4. Stop at a cause you can change. Five is a habit, not a rule. Stop when the next answer is outside your control; keep going if the last answer is still a symptom, a person, or “procedure not followed”. See why operator error isn’t a root cause.
5. Run the escape chain separately. Start from the control that should have caught the defect (the escape point) and ask why it missed it: method, frequency, limit sample or gauge capability.
6. Verify both root causes. Fill the verification box before you call D4 done.

The verification column

A 5 Whys chain finds candidate causes; it does not verify them. The evidence column is where the chain becomes proof. Two kinds of check usually work:

• Passive: data, logs, or a good-vs-bad comparison that match the time and place of the failure.
• Active: where safe and practical, switch the cause on and off and show the defect follows.

Do the same for the escape cause, for example by running known-bad parts through the check that missed them. “Team agreed” in this column means the cause isn’t verified yet.

Illustrative example: oversize bore (automotive machining)

This example is fictional and only shows how a filled template reads.

Verification: running a tool past the copied interval on a trial reproduced the oversize bore, and a fresh tool removed it (active). D5 then gets two actions: an interval set from wear data, and a check frequency tied to the drift rate.

The same structure works in other sectors: in PCBA assembly, a stencil with no wear limit (occurrence) and an inspection limit that let low deposits pass (escape); in food packing, a missing setup check after maintenance and a seal test run only at start-up. More examples are on weak D4 root cause examples.

Common misuse

• Only one chain: the escape is never asked.
• The first why is an assumption, so the whole chain rests on a guess.
• The evidence column is empty or says “team discussion”.
• The chain ends at a person, at training, or at “not followed”.
• Several branches are squeezed into one chain, so no answer follows from the one above.
• Open answers are left unmarked, and the next why is built on them.
• The D5 action doesn’t match the last why, which suggests the chain stopped in the wrong place.

Next, turn each verified cause into a D5 permanent corrective action. The full form is in the 8D report template, and the free printable 8D / D4 checklist (PDF) covers D1–D8 and goes deeper on D4.

FAQ

Is this the same as the fishbone vs 5 Whys page?

No. That page explains when to use each tool and how to combine them. This page is the 5 Whys worksheet itself and how to fill it in for D4.

Can I paste the filled template into our customer’s 8D form?

Yes, the table usually fits into D4. If the customer has its own form or customer-specific requirements (CSR), use their format and keep the evidence column.

What does 8D Gate check?

It gives a pre-send readiness check on the 8D text: an Accept / Conditional / Reject advisory with missing evidence and questions. It isn’t a customer decision. The review tool is v0.1: it reviews English 8D reports, and the interface and report are in English. Templates are also available in German, Czech and Polish.

Free pre-send readiness check

Before the 8D goes out, run the text through the free supplier 8D readiness check.

Get the free 8D / D4 checklist

Keep the one-page version next to your 5 Whys sheet. It covers D1–D8 and goes deeper on occurrence, escape, and verification.