Cause and Effect Diagram  Excel Template  Case Study

What is a Cause and Effect Diagram in 7 QC Tools?

→ It is a representation that 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 it in 1943 while consulting for Kawasaki steelworks in Kawasaki Shipyards so Dr. Joseph M. Juran named it as "Ishikawa".
→ This diagram is also known as a "Fishbone" because it looks like the bone of fish.

Fishbone

When we can use the Fishbone or Ishikawa:

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


What is a fishbone diagram used for?

  • It is used for root cause analysis.
  • Brainstorming
  • For check the relation between cause and effect

👉 Cause and Effect Diagram Excel Template Download




How to Make Constructing Fishbone Diagram? | Case Study

→ Four Steps are mentioned below:
  1. State the undesirable effect or problem
  2. Identify the main cause groups
  3. Arrange causes and sub-causes as relevant
  4. Identify potential root cause(s)

Step 1. State the undesirable effect or problem

→ First of all, we will mention the undesirable effect or problem and draw the backbone and a line.
→ Then 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.
→ For better understanding, we are taking one example for root_cause analysis for this we will prepare the backbone and line as mentioned in the below picture.

Step 1 State the undesirable effect or problem



Step 2. Identify the main cause groups

→ In the second step, we brainstorm the major categories of causes that are related to the problem.
→ For the manufacturing industry, it is "6M"
➨ In Manufacturing Industry "6M" stands for,
     ⇢ Man/People
     ⇢ Machine
     ⇢ Material
     ⇢ Method
     ⇢ Measurement
     ⇢ Mother Nature / Environment

Step 2 Identify the main cause groups

➨ For marketing Industry "6M" is replaced by "8P"
     ⇢ Product (or service)
     ⇢ Price
     ⇢ Promotion
     ⇢ Place
     ⇢ Process
     ⇢ People (personnel)
     ⇢ Physical evidence
     ⇢ Performance

➨ For Service Industry "6M"  is replaced by "4S"
     ⇢ Surroundings
     ⇢ Suppliers
     ⇢ System
     ⇢ Skill

→ Now we are taking an example of the poor mileage of cars to understand the concept of root cause analysis for this we are taking 6M then we will remove irrelevant "M" from "6M".


Step 3. Arrange causes and sub_causes as relevant:

→ Now we are moving forward by taking the problem of poor mileage in the car.
→ Write the categories of causes as branches from the main arrow
→ Brainstorm all the possible origins of the problem.
→ Ask: “Why does this happen?” As each idea is given, the facilitator writes it as a branch from the appropriate category.
→ Study all probable causes which are related to poor mileage of the car as mentioned below
     ⇢ Carburator adjustment
     ⇢ Underinflated tire
     ⇢ Poor maintenance
     ⇢ Poor driving habit
     ⇢ No awareness
     ⇢ Improper lubrication
     ⇢ Wrong fuel mixture
     ⇢ Engine oil grade is not proper
     ⇢ Gear shifting is not in sequence
     ⇢ Wrong gear shifting
     ⇢ Drive too fast

Step 3 Arrange causes and sub_causes as relevant



Step 4. Identify potential root_cause(s):

→ Again ask “why does this happen?” about each_cause.
→ Write all the things with the main branch and sub-branch.
→ Continue to ask “Why?” and generate deeper levels of problem origin.
→ After validation of all probability, we will get the reason for poor gas mileage in the car is poor maintenance of the car which you can easily understand from the below example.

Step 4 Identify potential root_cause

Benefits of Fishbone or Ishikawa

→ Helps to determine the root_cause
→ Increase Process Knowledge
→ Encourage group participation
→ A good tool for brainstorming
→ Identifies areas for collecting data

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