1. Method Name

5 Why (5 Why)

2. Alternative Names

Why-Why Analysis

3. Brief Description

5 Why is a simple yet effective technique for identifying the root cause of a problem (Root Cause Analysis). It involves repeatedly asking the question “Why?” until the underlying cause is identified, the elimination of which will prevent the problem from recurring.

4. Purpose / When to Use

It is used for troubleshooting, especially in less complex situations where it is necessary to quickly get past the surface of the symptoms. It is ideal for daily use directly on the Gemba to identify the causes of malfunctions, defects, delays, or safety incidents.

5. Procedure / How to Apply It

1. Define the problem: Clearly and concisely describe the problem that has occurred. For example, “Machine Z has stopped.”
2. Ask the first “Why?”: Why did the machine stop? -> Answer: Because the fuse blew. (First cause)
3. Ask the second “Why?”: Why did the fuse blow? -> Answer: Because the motor was overloaded. (Second cause)
4. Ask the third “Why?”: Why was the motor overloaded? -> Answer: Because the bearings were not sufficiently lubricated. (Third cause)
5. Ask the fourth “Why?”: Why weren’t the bearings sufficiently lubricated? -> Answer: Because the automatic lubrication system wasn’t working properly. (Fourth cause)
6. Ask the fifth “Why?”: Why wasn’t the lubrication system working? -> Answer: Because its filter was clogged and had not been inspected according to the maintenance schedule. (Root cause)
7. Propose a corrective action: Based on the root cause, define a solution (e.g., “Add inspection and cleaning of the lubrication system filter to the weekly autonomous maintenance schedule.”).

6. A Real-World Example

A customer complained that they received the wrong product. The team used the 5 Whys: 1. Why did the customer receive the wrong product? -> The shipping clerk packed the wrong item. 2. Why did the clerk pack the wrong item? -> He took it from the wrong shelf. 3. Why did he take it from the wrong shelf? -> The shelf label was unclear and similar to another one. 4. Why was the label unclear? -> It used a small font and was partially covered by a box. 5. Why wasn’t it corrected? -> There was no established process for regularly checking the visual labeling. Root cause: Lack of a verification process. Solution: Implement a weekly check of the legibility of all labels in the warehouse.

7. Benefits

- Simplicity: You don’t need statistical software or complex training
.- Speed: It allows you to quickly get to the heart of the problem.
- Promotes critical thinking: It teaches teams not to settle for the first, superficial cause
.- Low cost: All you need to apply it is a team of people and a flip chart.

8. Risks / Limits

- Over-simplification: With complex problems, there may be multiple root causes, and the 5 Whys method can lead to a single, incorrect conclusion.
- Dependence on the team’s knowledge: The quality of the result depends on the experience and knowledge of the people working on the analysis.
- Risk of assigning blame: “Why” questions can veer toward blaming individuals rather than identifying flaws in the process.
- The number “5” is a guideline: Sometimes 3 questions are enough; other times, 7 are needed. The team must not fixate on the number 5.

9. Practical Tips

- Always verify causality: After each answer, ask yourself a follow-up question in the opposite direction. For example, “If the filter hadn’t been clogged, would the machine have stopped?” This helps maintain a logical line of reasoning
.- Focus on processes, not people: Instead of “Why did John make a mistake?”, ask “Why did the process allow the mistake to happen?”
- Use it as a team: The analysis is more effective when more people with different perspectives participate
.- Combine it with a Gemba Walk: Conduct the 5 Whys analysis right where the problem occurred so you can verify the facts.