Hi, this is Mike Negami, Lean Sigma Black Belt.
Today, we’ll learn and practice how to use the Ishikawa Diagram and the 5-Why Analysis
in the Excel template.
Here are the steps: 1) Write down your problem statement.
2) Identify your large categories of process issues.
3) Break down each large category into smaller categories or factors.
4) Highlight the direct factors for your problem statement, and identify the root cause.
In Lean Sigma projects, we always aim for a fundamental resolution instead of temporary
solution so it's essential to find root causes.
Powerful tools for that are the Ishikawa Diagram (Cause and Effect Diagram), and the 5-Why
Analysis.
Click the link in this video's description, then you can download the Ishikawa Diagram's
Excel template.
This is the Ishikawa Diagram's screen.
It shows instructions here.
Read them later.
Because of its shape, it's also called a Fish Bone Diagram.
Gather supervisors of the target process and have a brainstorming session.
Step 1, put your project’s key problem statement in the head of the fish bone.
In my case study project, our Pareto Chart shows the top reason for product return was
“Customer's Cause”.
We need to find out the root cause of that.
Therefore, our problem statement will be “Why do customers return products with their own
fault as the excuse?”
Put that in the yellow box.
Step 2, put a large category in each large bone’s box.
The manufacturing industry has 4 M's as their framework for this: Man, Material, Machine
and Method.
In service operations, however, the 4 M's are usually not applicable.
Practically speaking, you start from asking “Please tell us large category factors for
the problem statement”.
Then, exchange opinions freely, narrow them down to 4 to 6 at most, then type them in
each blue box.
Step 3, break down the large categories into smaller categories or factors.
A great tool for this is the 5-Why Analysis.
For example, this large category is “Mistakes while taking orders”.
Then we’ll ask “Why did mistakes occur while taking orders?”
Likely responses might be: “An order was unclear” or “Unnecessary orders were made”
and so on.
Then, ask “Why did that happen?” for each answer.
“Why was the order unclear?”
“Why were unnecessary orders made?”
Repeat this at least 5 times.
This is the 5-Why Analysis.
However, at this point, you should not be concerned about connecting causal relationships
well.
Rather, it's better to get many opinions.
After all opinions were given, connect each answer by causal relationship.
A large bone is a result and a medium bone is a cause.
Then, the medium bone is a result and a small bone is a cause.
You may have smaller bones.
Put those relationships in the white boxes.
To save time, let's assume that my team gained these answers here.
I'll copy and paste them.
If a text is long, enlarge the box by dragging the edge of the box.
While pressing your shift key, click multiple boxes, then you can move them together.
Also, while pressing your control key, drag a box and release it.
You can copy it very easily.
Select only an arrow and drag only its top edge.
You can change its length and direction.
Do Step 3 for all of the large categories.
This is the completion of Step 3.
Step 4, discuss which are direct root causes for the problem statement, then highlight
them.
This is a “Root Cause Factor” card.
Use this as the highlight.
This is now completed.
The conclusion of this analysis is “Customers and sales reps didn't utilize the latest product
catalog well”.
Therefore, our solution is to utilize the latest product catalog more effectively.
Today we learned how to make the Ishikawa Diagram and the 5-Why Analysis.
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