Cause and Effect Diagram in 7 QC Tools | Ishikawa Diagram | Fish bone diagram in 7 QC Tools

Cause and Effect Diagram 7 QC Tools | Ishikawa Diagram or Fishbone diagram 

What is Cause and Effect Diagram?

Cause and Effect Diagram is a diagram which represents the meaningful relationship between an effect and its causes.
→It is a very good tool for root cause analysis and a part of 7 Basic Quality Control Tools.
→ Dr. Kaoru Ishikawa developed the first cause and effect diagram in 1943 while consulting for Kawasaki steelworks in Kawasaki Shipyards.
→ We can easily find out a valid root cause or causes by fishbone diagram or cause and effect diagram.

What is a Fishbone Diagram or Ishikawa Diagram?

→ A  cause and effect diagram is called a fishbone because it looks like the bone of fish.
→ Dr. Kaoru Ishikawa developed the first cause & effect diagram in 1943 while consulting for Kawasaki steelworks in Kawasaki Shipyards so Dr. Joseph M. Juran named it as "Ishikawa"

Fishbone or Ishikawa Diagram



Four Easy Steps for Constructing Cause and Effect Diagram in 7 QC Tools:

➤ Four Steps are mentioned below:

  1. State the undesirable effect or Problem
  2. Identify the main cause groups.
  3. then Identify causes and sub-causes.
  4. Identify potential root cause(s).


➥ Step 1. State the undesirable effect and draw the backbone and draw a line

Define a problem statement (effect)
→ Write it at the center-right of the chart or whiteboard. 
→ Draw a box around it and draw a horizontal arrow running to it.


Step1 Cause and Effect Diagram in 7 QC Tools



➥ Step 2. Identify the main cause groups

→ Brainstorm the major categories of causes of the problem. 
→ For manufacturing Industry, it is "6M"


➥  In Manufacturing Industry "6M" stands for in Fishbone Diagram or Ishikawa Diagram:

  1. Man/People
  2. Machine
  3. Material
  4. Method
  5. Measurement
  6. Mother nature / Environment
→ For marketing Industry "6M"  is replaced by "8P"


➥ In Marketing Industry "8P" stands for in Fishbone Diagram or Ishikawa Diagram:

  1. Product (or service)
  2. Price
  3. Promotion
  4. Place
  5. Process
  6. People (personnel)
  7. Physical evidence
  8. Performance
→ For Service Industry "6M"  is replaced by "4S"

➥ In Service Industry "4S" stands for in Fishbone Diagram or Ishikawa Diagram:

  1. Surroundings
  2. Suppliers
  3. System
  4. Skill
Step2 Cause and Effect Diagram in 7 QC Tools

➥ Step 3. Arrange causes and sub-causes suitably:

→ Write the categories of causes as branches from the main arrow
→ Brainstorm all the possible causes of the problem.
  Ask: “Why does this happen?” As each idea is given, the facilitator writes it as a branch from the appropriate category.

Step3 Cause and Effect Diagram in 7 QC Tools



➥ Step 4. Identify potential root cause(s):

→ Again ask “why does this happen?” about each cause. 
→ Write sub–causes branching off the causes. 
→ Continue to ask “Why?” and generate deeper levels of causes.
→ At last, you will get the Potential root cause.

Step4 Cause and Effect Diagram in 7 QC Tools

When we can use the Fishbone or Ishikawa:

→ When identifying possible causes for a problem
→ To identify all of the contributing root causes likely to be causing a problem
→ Especially when a team’s thinking patterns are different
→ This tool is very helpful during a Six Sigma Project


Benefits of Fishbone or Ishikawa: