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of asking why is generally sufficient to get to a root cause. The key idea of the method is to encourage the troubleshooter to avoid assumptions and logic traps and instead trace the chain of causality in direct increments from the effect through any layers of abstraction to a root cause that still
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root cause should point toward a process that is not working well or does not exist. Untrained facilitators without this understanding of the method often observe that answers obtained seem to point towards classical answers such as not enough time, not enough investments or not enough resources.
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or problem by repeating the question "why?" five times, each time directing the current "why" to the answer of the previous "why". The method asserts that the answer to the fifth "why" asked in this manner should reveal the root cause of the problem.
183:, described the five whys method as "the basis of Toyota's scientific approach by repeating why five times the nature of the problem as well as its solution becomes clear." The tool has seen use beyond Toyota, and is now used within
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The five whys technique has been criticized as a poor tool for root cause analysis. Teruyuki
Minoura, former managing director of global purchasing for Toyota, criticized it as being too basic a tool to analyze
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has some connection to the original problem. In this example, the fifth "why" suggests a broken process or an alterable behavior, which is indicative of reaching the root-cause level.
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76:. Others at Toyota and elsewhere have criticized the five whys technique for being too basic and having an artificially shallow depth as a root cause analysis tool (see
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Medical professor Alan J. Card also criticized the five whys as a poor root cause analysis tool and suggested that it be abandoned because of the following reasons:
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These answers regardless of merit are often out of the troubleshooter's control to fix. Therefore practitioners of the method recommend instead of asking
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The five whys is based on a misguided reuse of a strategy to understand why new features should be added to products, not a root cause analysis.
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Inability to go beyond the investigator's current knowledge – the investigator cannot find causes that they do not already know.
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Results are not repeatable – different people using five whys come up with different causes for the same problem.
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This nature of the answer to the fifth why in the example is an important aspect of the five why approach. The
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Tendency to isolate a single root cause, whereas each question could elicit many different root causes.
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The questioning for this example could be taken further to a sixth, seventh, or higher level, but five
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relationships underlying a particular problem. The primary goal of the technique is to determine the
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Tendency for investigators to stop at symptoms rather than going on to lower-level root causes.
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To avoid these issues, Card suggested instead using other root cause analysis tools such as
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at the depth necessary to ensure an issue is fixed. Reasons for this criticism include:
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These tools allow for analysis to be branched in order to provide multiple root causes.
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Ask why. Ask it all the time, ask it any day, and always ask it three times in a row.
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Lack of support to help the investigator provide the right answer to "why" questions.
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during the evolution of its manufacturing methodologies. It is a major component of
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The artificial depth of the fifth why is unlikely to correlate with the root cause.
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Two primary techniques are used to perform a five whys analysis: the
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An example of a problem is: the vehicle will not start.
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Toyota production system: beyond large-scale production
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training, delivered as part of the induction into the
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In other companies, it appears in other forms. Under
410:Serrat, Olivier (2017). "The Five Whys Technique".
556:"5-whys Analysis using an Excel Spreadsheet Table"
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179:. The architect of the Toyota Production System,
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472:""Ask 'why' five times about every matter.""
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389:. Portland, OR: Productivity Press.
350:Olivier D., Serrat (February 2009).
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586:. October 8, 2003. Archived from
295:Eight disciplines problem solving
27:Iterative interrogative technique
68:The technique was described by
532:Bulsuk, Karn (April 2, 2009).
224:fishbone (or Ishikawa) diagram
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773:Total productive maintenance
758:Single-minute exchange of die
743:Continuous-flow manufacturing
615:Card, Alan J. (August 2017).
554:Bulsuk, Karn (July 7, 2009).
470:Ohno, Taiichi (March 2006).
420:10.1007/978-981-10-0983-9_32
617:"The problem with '5 whys'"
582:. Public Affairs Division,
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534:"An Introduction to 5-why"
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636:10.1136/bmjqs-2016-005849
154:why did the process fail?
814:Toyota Production System
738:Muri - Standardized work
622:BMJ Quality & Safety
584:Toyota Motor Corporation
356:. Asian Development Bank
177:Toyota Production System
169:Toyota Motor Corporation
167:and was used within the
74:Toyota Motor Corporation
30:Not to be confused with
804:Problem solving methods
353:The Five Whys Technique
302:(information-gathering)
718:Cellular manufacturing
504:The Seven-Day Weekend
443:Fantin, Ivan (2014).
593:on November 21, 2020
414:. pp. 307–310.
331:Why–because analysis
52:used to explore the
768:Production leveling
412:Knowledge Solutions
321:Root cause analysis
109:is not functioning.
809:Lean manufacturing
728:Muda - Over burden
706:Lean manufacturing
189:lean manufacturing
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783:Plan–do–check–act
733:Mura - Unevenness
429:978-981-10-0982-2
193:lean construction
115:– The alternator
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508:. Penguin.
306:Four causes
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119:has broken.
798:Categories
337:References
316:Issue tree
218:Techniques
137:iterations
107:alternator
58:root cause
763:Poka-yoke
753:Five whys
723:Takt time
311:Issue map
237:Criticism
197:Six Sigma
50:technique
46:iterative
38:Five whys
653:42544432
645:27590189
500:(2004).
381:(1988).
289:See also
279:fishbone
99:is dead.
44:) is an
300:Five Ws
159:History
152:to ask
97:battery
84:Example
32:Five Ws
748:Kanban
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226:and a
185:Kaizen
105:– The
95:– The
62:defect
42:5 whys
18:5 whys
708:tools
649:S2CID
591:(PDF)
580:(PDF)
60:of a
641:PMID
599:2019
563:2019
541:2019
510:ISBN
484:2019
451:ISBN
424:ISBN
391:ISBN
362:2019
210:and
195:and
150:why?
145:real
129:Why?
123:Why?
117:belt
113:Why?
103:Why?
93:Why?
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