5 Why Analysis: Root Cause Technique & Example
Definition
The 5 Whys is a root cause analysis technique in which a team asks 'why?' repeatedly — typically about five times — starting from a problem, until it reaches a cause that, if fixed, stops the problem coming back.
| Term | 5 Whys (root cause analysis) |
|---|---|
| In Hindi | 5 क्यों विश्लेषण |
| Area | Production & quality |
| Search phrase | 5 why analysis |
| Try it | Fishbone diagram |
5 क्यों विश्लेषण — हिंदी में अर्थ
5 क्यों (5 Whys) मूल कारण विश्लेषण की तकनीक है जिसमें टीम किसी समस्या से शुरू करके बार-बार 'क्यों?' पूछती है — आमतौर पर लगभग पाँच बार — जब तक ऐसा कारण न मिल जाए जिसे ठीक करने पर समस्या दोबारा न आए।
How to run a 5 Why analysis
Write the problem precisely — what, where, when, how much. Go to the place (gemba) and look at the part or machine. Ask why it happened and write an answer backed by facts, not opinion. Ask why again of that answer. Stop when the answer is a process or system cause you can control, and check the chain backwards with 'therefore'.
Five is a guide: sometimes three whys reach the root, sometimes seven. Separate chains may be needed for 'why did it happen' and 'why was it not detected'.
Common mistakes
Stopping at 'operator error' — ask why the process allowed the error. Guessing instead of checking. Following only one branch when there are several causes; a fishbone diagram first helps list them. Ending with an action like 'retrain operator' instead of a lasting fix such as a poka-yoke, an SOP change or a PM checklist item. The result feeds directly into the corrective action of a CAPA.
Example
Why did the conveyor motor trip? Overload. Why? The gearbox bearing seized. Why? It was not lubricated. Why? It is not on the lubrication chart. Why? The chart was not updated when the gearbox was replaced last year. Fix: add it to the chart and make chart updates part of every equipment change.
Related tools and guides
Frequently asked questions
What is 5 Why analysis?
A technique of repeatedly asking 'why?' to move from a problem's symptom to its root cause.
Who invented the 5 Whys?
It is credited to Sakichi Toyoda and was made widely known through the Toyota Production System.
Is 5 Why the same as why-why analysis?
Yes, Indian plants often call it why-why analysis.
When should 5 Whys not be used alone?
For complex problems with many interacting causes — combine it with a fishbone diagram or data analysis.
Related terms
- 5S5S is a workplace organisation method with five steps: Sort (Seiri), Set in order (Seiton), Shine (Seiso), Standardise (Seiketsu) and Sustain (Shitsuke).
- CAPA (Corrective and Preventive Action)CAPA stands for Corrective and Preventive Action — a structured process to find the root cause of a quality problem, fix it so it does not recur (corrective), and stop similar problems before they occur (preventive).
- DMAIC (Six Sigma)DMAIC — Define, Measure, Analyse, Improve, Control — is the five-step, data-driven problem-solving method used in Six Sigma to improve an existing process by finding and removing the root causes of defects and variation.
- First pass yield (FPY)First pass yield (FPY) is the percentage of units that pass a process step correctly the first time, without rework, repair or scrap. FPY = units passed first time ÷ units entering the step × 100.
- Fishbone diagram (Ishikawa)A fishbone diagram, also called an Ishikawa or cause-and-effect diagram, lays out all the possible causes of a problem in categories along the 'bones' of a fish whose head is the problem, so that a team can brainstorm and then test the likely ones.
- Job workJob work means processing of goods belonging to another registered person (the principal) — such as machining, plating, painting or heat treatment. Under GST, the principal can send goods to a job worker on a challan without paying tax, if they come back in time.