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5 Whys Root Cause Tool

Define the problem, ask why with evidence at each step, test the logic in reverse, then set actions and check they worked. Supports the Analyse phase of the DMAIC project board.

How to use this tool

• Define the problem with what, where, when and how big. A vague problem gives a vague root cause.
• Answer each why from evidence, not opinion. Go and look at the process, then tick how you know.
• Five is a guide. Stop when you reach a cause in the process or system that you can fix. Add or remove whys as needed.
• Watch for blame. If the answer is a person, ask why the system allowed it.
• Test in reverse. Read the chain from the root cause back to the problem. If the root cause were fixed, would the problem have been prevented?
• Close the loop with containment, corrective and preventive actions, and a measure to verify the fix held.
• If the problem has several causes, use a fishbone first and run one 5 Whys per branch.

1. Problem statement

Process / line / area

Date raised

Owner / facilitator

What is the problem? (specific, factual)

How big is it? (count, rate, cost, or impact)

2. The whys

+ Add another why

3. Root cause and logic check

Root cause statement (a process or system gap you can fix)

Root cause category Select Standard work or procedure Training or skills system Equipment or tooling Material or supply Method or process design Measurement or inspection Management or ownership Environment or layout

Reverse test: if this were fixed, would the problem have been prevented? Select Yes, the chain holds Unsure, needs more evidence No, re-check the whys

4. Actions

Action	Type	Owner	Due	Status

+ Add action

5. Verify it worked

Measure that proves the fix held

Target

Check date

Result

Outcome Not yet checked Effective, standardise Partly, revisit the whys Not effective, restart

Completeness check

5 Whys Root Cause Tool · Continuous Improvement toolkit.
Data saves automatically in this browser only. It will not appear on another device or browser. Use Export backup and Import backup to move an analysis between them. The example is based on a real stoppage on Line 8.