5 Whys Analysis
The 5 Whys is a simple root cause analysis technique that repeatedly asks why a problem occurred until the team reaches an evidence-supported and actionable underlying cause.
What this term means in maintenance
The 5 Whys is a simple root cause analysis technique that repeatedly asks why a problem occurred until the team reaches an evidence-supported and actionable underlying cause.
How the 5 Whys works
The team begins with a clearly defined problem and asks why it happened. Each supported answer becomes the basis for the next question. Five is a guide, not a fixed requirement.
Practical example
Problem: A pump stopped.
- Why did it stop? The motor overload tripped.
- Why did the overload trip? The pump shaft required excessive torque.
- Why was the torque excessive? The bearing had seized.
- Why did the bearing seize? Water entered the bearing housing.
- Why did water enter? The seal was damaged and seal condition was not included in routine inspection.
The action should address the seal condition and inspection control, not only replace the bearing.
When to use it
The 5 Whys works best for relatively straightforward problems with a traceable cause path. It is useful during daily problem-solving, repeat-failure review, and corrective-action discussions.
When it is not enough
Complex systems may contain several interacting causes. High-consequence incidents may require evidence preservation, specialist analysis, multiple cause branches, or a more formal investigation method.
Common mistake
The answers must be supported by evidence. A confident sequence of assumptions is not a root cause analysis.
Related concepts
Related maintenance terms
Keep exploring connected CMMS, reliability, and maintenance planning terms.
Root Cause Analysis
Root cause analysis is a structured investigation used to identify the underlying conditions that allowed a failure or problem to occur and determine actions that reduce recurrence.
Fishbone Diagram
A fishbone diagram is a cause-and-effect analysis tool used to organize possible causes of a problem into logical categories before evidence is used to confirm the real causes.
Fault Tree Analysis
Fault tree analysis is a deductive method that starts with an unwanted event and maps the combinations of equipment, process, control, or human failures that could cause it.
Glossary FAQs
- Does the method require exactly five questions?
No. Ask as many evidence-supported questions as needed to reach an actionable underlying cause.
- When should the 5 Whys not be used alone?
Do not rely on it alone for complex systems, multiple interacting causes, or high-consequence incidents requiring deeper evidence review.
- Can a 5 Whys analysis have more than one branch?
Yes. A problem may require separate cause paths covering equipment, methods, people, materials, controls, and operating conditions.