KaizenProof

Lesson 5 of 23 · 6 min read

The 5 Whys: ask why until you reach something you can change

In Lean: 5 Whys

Builds on: Errors and rework, Work nobody uses, Extra steps, Skills not used

In one minute

The 5 Whys is a way to get from a symptom to a cause you can change. You start from one specific problem, ask why it happens, then ask why about that answer, and keep going. You stop when you reach something in the process the team can change: a rule, a missing tool or link between tools, an unclear owner, information that is missing at the start. If a chain ends at a person, it has not finished.

The idea

Many fixes fail because they treat the symptom. Invoices are paid late, so someone sends reminders. The reminders help for a while, then become one more thing to chase. Asking why several times in a row is a simple discipline that pushes past the first, obvious answer.

How to run it:

  1. Start from one specific problem. "Supplier invoices for the warehouse are paid after the due date", not "finance is a mess". A vague start produces vague answers.
  2. Ask why it happens, and write the answer down as a fact. Each answer should be something you could check by looking at the work: an email, a form, a system setting.
  3. Ask why about that answer, using its own words, so the chain stays connected.
  4. Stop at something the team can change. A rule or policy, a missing tool or integration, an unclear owner, information missing at the start of the process. That is the cause you can change (in Lean: root cause), where a countermeasure can take hold.
The 5 Whys, from symptom to a cause you can changeAsk why about each answer, in its own words, until the answer is something in the process the team can change.

Illustrative example, not real data

A 5 Whys chainA chain of six boxes, read top to bottom, each joined to the next by an arrow labelled why. Problem: Warehouse invoices are paid after the due date. Why 1: They wait days for approval. Why 2: Approval needs the order, and the order is not in the system yet. Why 3: Orders are keyed in only after the goods arrive. Why 4: Orders are placed by phone, with no record made at the time. Why 5: No step in ordering creates the order record. The last answer is marked: stop here, a gap you can change. An arrow runs back up the right side: read the chain from the cause to the problem, joining each line with and therefore.ProblemWarehouse invoices are paidafter the due datewhy?Why 1They wait days for approvalwhy?Why 2Approval needs the order, and theorder is not in the system yetwhy?Why 3Orders are keyed in only afterthe goods arrivewhy?Why 4Orders are placed by phone, withno record made at the timewhy?Why 5No step in ordering createsthe order recordStop here: a gap you can changeread back: “and therefore”
  • Stop when the answer names a gap you can change: a rule, a tool, an owner, or information missing at the start.
  • If an answer names a person (“the buyer forgets”), ask what in the process lets it happen.
  • Five is a rule of thumb. Stop sooner when you reach the cause; go on when you have not.

Five is a rule of thumb, not a quota. Some chains reach a changeable cause in three steps; some need six. Stopping at a real cause is better than inventing two more whys to reach five.

Two checks keep a chain honest. Read it backwards, from the cause to the problem, joining each line with "and therefore": if a link sounds wrong, a step is missing or guessed. Then ask whether changing the last answer would stop the problem from coming back. If not, keep going.

When a chain reaches a person, redirect it. "Because the buyer forgets to send the order" describes what happened; it is not a cause. Turn the question to the process: what makes this depend on someone remembering? Anyone in that role would forget sometimes, on a busy week. The answer, "nothing triggers the order; it goes out only when someone thinks of it", is something the team can change, and nobody is blamed.

Example

Illustrative example, not a real company.

Problem: employees wait around two weeks for an employment confirmation letter, often needed for a rental or a mortgage.

  • Why? Requests sit in one payroll specialist's personal inbox until there is time for them.
  • Why only that inbox? Only payroll can see the salary data the letter needs, and requests have no shared queue.
  • Why is there no other way to get a letter? The template was set up inside the payroll system long ago, and nobody ever decided who else may produce letters, or whether employees could generate their own.

Three whys. The cause the team can change: nobody owns the confirmation-letter process, so there is no shared queue and no self-service template. A chain that stopped at "the payroll specialist is slow" would have led nowhere. She is one person doing an extra job the process put on her.

Common mistakes

  • Ending at a person. "Because the clerk made a mistake." Ask what in the process makes that mistake easy or likely.
  • Ending at "lack of time" or "not enough people". Too general to act on. Ask where the time goes and why.
  • Ending at a guess. "Probably because the system is slow at month end." Check it before building on it; a chain built on a guess leads to the wrong fix.

Words to know

  • Asking why until you reach something you can change (in Lean: 5 Whys).
  • The cause you can change (in Lean: root cause): the point in the process where a change stops the problem from coming back.
  • Symptom: what you notice; the problem the chain starts from.

Check your understanding

3 questions. Answer them all, then check. You can try again as often as you like; nothing about your attempts is kept.

Question 1 of 3Three teams asked why customer refunds go out late. Which chain is flawed?
Question 2 of 3New joiners lack system access on day one. Why? Access requests are raised only once they start. Why? Nothing raises them earlier. Why? No step in onboarding requests access when the offer is signed. Where should this chain stop?
Question 3 of 3A chain reads: 'Purchase orders reach suppliers late. Why? Because the buyer forgets to send them.' What is the best next question?

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Try it on your own work

Describe one recurring task that wastes your time, and see these ideas applied to it.

Report a friction (opens in a new tab)

Worksheet for this lesson: 5 Whys Template (free download, no sign-up).

Where this comes from

Asking why repeatedly is closely associated with the Toyota Production System, where it was used on the shop floor to get past symptoms to causes; it is now used across the Lean and quality traditions.