Ishikawa Cause-and-Effect Diagram
Explore possible causes systematically, organise them into meaningful branches and distinguish hypotheses from causes confirmed by evidence.
Purpose and method
Collect and organize potential causes in a fishbone diagram using structured categories such as the 6M.
When to use it
Use Ishikawa during team analysis when the problem may have several interacting technical and organizational causes.
Core principle
A fishbone diagram expands the search space; it does not prove causation. Its value comes from prioritising and testing the most credible branches.
What the interactive module provides
- Fishbone diagram
- Categorized causes
- Highlighted root-cause candidates
- structured cause map, prioritised hypotheses and verification plan
Professional verification: The module supports learning, analysis and documentation. Verify results against actual process conditions, internal standards, safety requirements and competent professional judgement before implementation.
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Recommended workflow
Explore possible causes systematically, organise them into meaningful branches and distinguish hypotheses from causes confirmed by evidence.
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Write one measurable effect at the head
- 2
Choose categories suited to the process
- 3
Generate causes at the gemba with a cross-functional team
- 4
Break broad causes into testable sub-causes
- 5
Prioritise, test and mark confirmed or rejected causes
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Practical example
For variable weld penetration, the team maps machine, method, material, measurement, people and environment causes, then tests current calibration and gas-flow stability first.
Calculation or verification principle
No equation is required. Rank hypotheses by impact, likelihood and ease of verification, then record test results directly against each branch.
Required inputs → Expected outputs
- Required inputs
- clear effect statement, process knowledge, observations, data and candidate cause categories
- Expected outputs
- structured cause map, prioritised hypotheses and verification plan
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Common mistakes to avoid
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Treating categories as a mandatory checklist
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Listing solutions instead of causes
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Choosing causes by voting alone
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Ending the analysis when the diagram looks full
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Frequently asked questions
What data do I need to use this tool?
Prepare clear effect statement, process knowledge, observations, data and candidate cause categories.
What result does the module produce?
The module produces structured cause map, prioritised hypotheses and verification plan.
Can I implement the result without further review?
No. Treat the output as a structured engineering and improvement aid. Verify source data, assumptions, safety, quality, legal requirements and local process conditions with competent responsible people before implementation.
LEAN Toolbox
Open interactive tool →Ishikawa Cause-and-Effect Diagram
Explore possible causes systematically, organise them into meaningful branches and distinguish hypotheses from causes confirmed by evidence.