5 Whys

5 Whys is a structured root cause analysis technique that investigates a problem by repeatedly asking the question “Why?” to move from a visible symptom to underlying causes.

In manufacturing and other process-based environments, the 5 Whys method is typically applied as follows:

• 1. Define the problem clearly: State the specific defect, breakdown, or incident in factual, measurable terms.
• 2. Ask the first “Why?”: Identify the immediate, observable cause of the problem.
• 3. Ask subsequent “Why?” questions: For each answer, ask “Why did this happen?” and record the next-level cause. This is repeated in a logical chain, often around five times, until a controllable, process-level cause is identified.
• 4. Validate each link with evidence: Check data, records, and observations to confirm that each stated cause actually occurred and can reasonably produce the next effect in the chain.
• 5. Identify root cause(s): Stop when the cause is specific, actionable within the system or process, and no further “Why?” yields new, verifiable information.

The number of iterations is not fixed; more or fewer than five questions may be used. The technique is often performed by a small cross-functional team familiar with the process, documented step by step, and integrated with broader Root Cause Analysis activities and corrective action planning.