Tool 25: Cause and Effect Diagram (CED)

AKA

Fishbone Diagram, Ishikawa Diagram

Classification

Analyzing/Trending (AT)

Tool description

The cause and effect diagram is a fishbone diagram that typically displays major, generic categories such as people, methods, materials, equipment, measurement, and environment that cause an effect, often perceived as a problem. First applied by Kaoru Ishikawa in 1950, this diagram is used to systematically analyze cause and effect relationships and to identify potential root causes of a problem.

Typical application

• To assist a team to reach a common understanding of a complex problem.

• To expand the team's thinking and consider all potential causes.

• To define the major categories or sources of root causes.

• To organize and analyze relationships and interactive factors.

• To identify factors that could improve a 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
	Creativity/innovation
	Engineering
	Project management
3	Manufacturing
	Marketing/sales
	Administration/documentation
2	Servicing/support
4	Customer/quality metrics
1	Change management

links to other tools

before

• Brainstorming

• Five Whys

• Brainwriting Pool

• 5W2H method

• 6-3-5 Method

after

• Problem Specification

• Work Flow Analysis (WFA)

• Pareto Chart

• Countermeasures Matrix

• Problem Analysis

Notes and key points

• Generic category designation may be substituted. Example: "procedures" for "methods," or "facilities" for "equipment," etc.

• Do not overload categories. Establish another category if more detail is desired.

Step-by-step procedure

• STEP 1 Reach consensus on a problem to be analyzed. See example Missed Reproduction Schedules.

• STEP 2 Determine the major categories and place one in each category box.

• STEP 3 Brainstorm possible causes for each category and enter them in a fishbone fashion by drawing arrows to the main arrow (category) as shown in the example.

• STEP 4 Continue to ask questions using the Five Whys tool to search for root causes. Insert and connect potential causes to the various other contributing factors.

• STEP 5 When ideas or causes can no longer be identified, further analyze the diagram to identify additional data collection requirements for problem solving.

Example of tool application