5 Whys

Five Whys5 Why’s5-whysfive whys' technique
5 Whys is an iterative interrogative technique used to explore the cause-and-effect relationships underlying a particular problem.wikipedia
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Sakichi Toyoda

his father
The technique was originally developed by Sakichi Toyoda and was used within the Toyota Motor Corporation during the evolution of its manufacturing methodologies.
Toyoda developed the concept of 5 Whys: When a problem occurs, ask "why" five times to try to find the source of the problem, then put into place something to prevent the problem from recurring.

Eight disciplines problem solving

Eight Disciplines Problem Solving
D4: Determine and Verify Root Causes and Escape Points: Identify all applicable causes that could explain why the problem has occurred. Also identify why the problem was not noticed at the time it occurred. All causes shall be verified or proved. One can use five whys or Ishikawa diagrams to map causes against the effect or problem identified.

Kaizen

Continuous improvementJapanese kaizenKaizen (continuous improvement)
The tool has seen widespread use beyond Toyota, and is now used within Kaizen, lean manufacturing and Six Sigma.
Another technique used in conjunction with PDCA is the 5 Whys, which is a form of root cause analysis in which the user asks a series of five "why" questions about a failure that has occurred, basing each subsequent question on the answer to the previous.

Root cause analysis

root cause analysesRoot CausesRoot-cause analysis
Root cause analysis
Define and describe properly the event or problem ('five whys' technique).

Ishikawa diagram

cause-and-effect diagramfishbone diagramcause and effect diagram
the fishbone (or Ishikawa) diagram
Each potential cause is traced back to find the root cause, often using the 5 Whys technique.

Five Ws

Circumstanceswho, what, when, where, why and how5 W
Five Ws (information-gathering)
Starting in the 2000s, the Five W's were sometimes misattributed to Kipling, especially in the management and quality literature, and contrasted with the 5 Whys.

Skill

skillscompetencetalent
5 Whys is an iterative interrogative technique used to explore the cause-and-effect relationships underlying a particular problem.

Causality

causalcausationcause and effect
5 Whys is an iterative interrogative technique used to explore the cause-and-effect relationships underlying a particular problem.

Root cause

root-cause(root) causesroot
The primary goal of the technique is to determine the root cause of a defect or problem by repeating the question "Why?".

Defect

defectsdefective
The primary goal of the technique is to determine the root cause of a defect or problem by repeating the question "Why?".

Iteration

iterativeiterativelyiterated
The questioning for this example could be taken further to a sixth, seventh, or higher level, but five iterations of asking why is generally sufficient to get to a root cause.

Toyota

Toyota Motor CorporationToyota MotorToyota Store
The technique was originally developed by Sakichi Toyoda and was used within the Toyota Motor Corporation during the evolution of its manufacturing methodologies.

Toyota Production System

20th Centuryproduction systemToyota
It is a critical component of problem-solving training, delivered as part of the induction into the Toyota Production System.

Taiichi Ohno

Ohno, Taiichi
The architect of the Toyota Production System, Taiichi Ohno, described the 5 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."

Lean manufacturing

Leanlean productionindustrial efficiency
The tool has seen widespread use beyond Toyota, and is now used within Kaizen, lean manufacturing and Six Sigma.

Six Sigma

Lean Six SigmaSix Sigma (6σ) Six Sigma Black Belt Certification
The tool has seen widespread use beyond Toyota, and is now used within Kaizen, lean manufacturing and Six Sigma.

Ricardo Semler

Under Ricardo Semler, Semco practices "three whys" and broadens the practice to cover goal setting and decision making.

Necessity and sufficiency

necessary conditionnecessary and sufficient conditionsufficient condition
In addition, performing logical tests for necessity and sufficiency at each level can help avoid the selection of spurious causes and promote the consideration of multiple root causes.

Socratic method

Socraticmaieuticelenchus
Socratic method

The Lean Startup

Lean StartupThe Lean Startup: How Today's Entrepreneurs Use Continuous Innovation to Create Radically Successful Businesses
Ries also recommends using a process called the Five Whys, a technique designed to reach the core of an issue.

Accident

accidentsmisadventurefreak accident
Ishikawa diagrams are sometimes used to illustrate root-cause analysis and five whys discussions.