Tool 77: Five Whys

AKA

Root Cause Analysis

Classification

Analyzing/Trending (AT)

Tool description

The five whys uses a systematic questionnaire technique to search for root causes of a problem. The technique requires participants to ask "why?" at least five times, or work through five levels of detail. Once it becomes difficult to respond to "why?," the probable cause may have been identified.

Typical application

• To identify the reason(s) for an abnormal condition or situation.

• To identify the root causes (s) of a problem.

• To start a data collection process.

Problem-solving phase

→	Select and define problem or opportunity
→	Identify and analyze causes or potential change
	Develop and plan possible solutions or change
	Implement and evaluate solution or change
	Measure and report solution or change results
	Recognize and reward team efforts

Typically used by

	Research/statistics
3	Creativity/innovation
	Engineering
4	Project management
	Manufacturing
	Marketing/sales
	Administration/documentation
	Servicing/support
2	Customer/quality metrics
1	Change management

links to other tools

before

• Tree diagram

• Checksheet

• Cause and effect diagram (CED)

• Defect map

• Problem specification

after

• Countermeasures matrix

• Shewhart PDCA cycle

• Force field analysis (FFA)

• Gap analysis

• Action plan

Notes and key points

• While asking "five whys," do not switch to asking "who." The focus is on the process of the problem, not the person involved.

• Continue to ask "why" beyond the arbitrary five times if necessary to get to the root cause of a problem

Step-by-step procedure

• STEP 1 Complete a problem statement by describing a perceived problem in specific terms. See example The Night Shift Productivity Output Is Often Lower than That of the Day Shift.

• STEP 2 Ask the first "why" question. Why does this problem exist?

• STEP 3 Continue to ask "why" questions until the root causes are identified. This process may take more than "five whys"!

• STEP 4 Write a next step statement for solving the problem.

Example of tool application

State a (perceived) problem: Date: xx/xx/xx
The night shift productivity output is often lower than that of the day shift.
Ask "Why" 1	Why is productivity lower on the night shift?
Response:	Punch presses model X are frequently switched off by quality inspectors.
Ask "Why" 2	Why are these particular presses switched off?
Response:	Nightshift operator cannot calibrate model X presses.
Ask "Why" 3	Why cannot operators maintain and calibrate this model?
Response:	The operators have not been trained on this model.
Ask "Why" 4	Why were operators not trained on this model?
Response	Some presses of this model were recently placed into service. Factory training was provided to day shift operators.
Ask "Why" 5	Why did night shift operators not receive this training?
Response:	The training department does not have update training in the punch press workshop.
Root cause(s) of the perceived problem identified?
Yes. Punch press model X is presently not covered in the company's training program for operators. All PP model X operators need update training.