Fishbone diagram(Ishikawa) or cause and effect diagram
Learn how to do cause and effect analysis and present it in terms of a Fishbone. Fishbone is also known as cause and effect diagram or Ishikawa diagram. Examples presented here will help you to understand the concept and you can also use the same template for your project.
Cause and effect is a systematic approach to explore various causes leading to a problem condition, It is a group activity in which all the stakeholders brainstorm around a problem condition. This problem condition is the “Y” and is also called the “effect”. The final output of the activity resembles a Fishbone – hence it is also commonly called a Fishbone Diagram. The “effect” forms the head of the fish and causes form the bones.
There are four steps to construct a cause and effect diagram
Step1: Brainstorm all possible causes of the problem or effect selected for analysis:
It is a group activity and subject matter experts should be involved, the Black Belt can facilitate the brainstorming. List down all the causes on a board.
Step2: Classify the major causes under the heading 6 M’s or 4 P’s or any thing :
In the previous step we listed all the possible causes which are impacting the “Y” or the problem. But many of these potential causes might be having a very small impact on Y, so we need to prioritize and shortlist the potential causes. We can use multivoting to shortlist the potential causes.
After shortlisting the potential causes we need to categorize them into 6 M’s or 4 P’s, explained later in the article.
Step3: Draw a cause and effect diagram:
Once we have the categorization ready we need to put it on the Fishbone diagram
Step4: Find root cause for each potential X:
Once we have put all the causes in the respective categories, the next step is to do Why? Why? Analysis to reach the root cause for each potential cause. This is a very important step and Why-Why tool is a very simple but effective method of finding root causes.
Build at least a level-3 fishbone (ask Why? Why? Why? ), The Middle Bones indicates the direction of path from cause to effect, each issue is addressed till the 5th WHY/3rd Why (What is 5 Why analysis)
First of all let me tell you that there is no hard and fast rule over the categorization of the bones in a Cause and Effect diagram. You can categories as per what is suitable in your business case.
I am going to talk about two templates which can be termed as best practices and can be used in most of the situations.
6 M’s – Man, Method, Mother nature, Measurement, Machine and Material
This is the most widely used template and these 6 categories cover all aspects of any problem. I have explained all the six categories in the example below.
Other one that is widely used is the 4 P’s.
4 P’s – People, Process, Policies and Plant
People is nothing but Man as per 6 M, Process is Method of 6 M,
Policies are company policies like HR policies, work policies or can be government policies as well. We cover policies under Method only of 6 M.
Plant covers basically your machine, material as well as the work environment.
Other than these two templates, you can create one basis different functions like Design, HR, Operations etc. You can create these templates very easily in PPT or Excel. I like creating them in PPT format and are essential part of my project packs.
“ what is 6M in Fishbone?
Example: Fish Bone Analysis-Breakdown conversion
I hope you now understand what should go under which bone or category. Just check the example given below, it will remove rest of the doubts if any.
In this example, Y is mentioned as “Decrease in breakdown conversion%” as head of the fish. Then M1-M11 are the 1st level causes, you can number them or leave them without numbering.
X1-X19 are the root causes for each M, your fishbone can have further drill down as well. It is a good practice to give an identifier like x1—x10 to each root cause.
As the team could not find any cause related to work environment so Mother Nature category is enmpty.
“Why-Why” Analysis helps to structure brainstormed ideas towards problem root causes.
When to Use it When the team needs to explore possible root causes and represent them on a single diagram.
How to Use it
1. State the problem to be analyzed.
2. Ask “Why” – i.e.. what are the first level of causes of the problem?
3. Write each cause on the diagram.
4. For each cause, ask “Why” again and write the answers in the next
column, linked to the previous answer.
5. Keep asking “Why” until no more answers can be suggested.
6. Use the causes listed, especially those on the last level of the diagram,
to generate possible solutions.
7. Review data for evidence of which causes are most important; gather
fresh data if necessary.
I hope you have understood the Fishbone tool and if you want to learn more such tools then go for a Six Sigma course from Simplilearn. The course is aligned to IASSC and ASQ exam, integrates lean and DMAIC methodologies using case studies and real-life examples.
There is another good online GB course from Coursera. This course is from University System of Georgia and it has very good reviews as well.
Do check other data science related courses as well, Python is becoming very popular for machine learning and industry demand is very high.
There are great online courses available for Six Sigma, PMP, Data Science, Big Data, Machine Learning and Python.
If you want to have a course from a recognized university then Coursera is the place for you. Otherwise I would recommend Simplilearn.
Simplilearn certificate is well recognized in the industry and courses are really helpful.
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