1. Determine the Root Cause
- Five Whys & Robert Xiong’s Approach
Robert Xiong
May 29, 2014

2. What is the 5 Whys
The 5-Whys is a simple approach for exploring root causes and instilling a “Fix the root
cause, not the symptom,” culture at all levels of a company. Invented by Japanese
Industrialist Sakichi Toyoda, the idea is to keep asking “Why?” until the root cause is
arrived at.
By repeatedly asking the question “Why” (five is a good rule of thumb), you can peel
away the layers of symptoms which can lead to the root cause of a problem. Very often
the ostensible reason for a problem will lead you to another question. Although this
technique is called “5 Whys,” you may find that you will need to ask the question fewer
or more times than five before you find the issue related to a problem.
Benefits of the 5 Whys
• Help identify the root cause of a problem.
• Determine the relationship between different root causes of a problem.
• One of the simplest tools; easy to complete without statistical analysis.
When Is 5 Whys Most Useful?
• When problems involve human factors or interactions.
• In day-to-day business life; can be used within or without a Six Sigma project.

3. How to Complete the 5 Whys
1.Write down the specific problem. Writing the issue helps you formalize
the problem and describe it completely. It also helps a team focus on the
same problem.
2.Ask Why the problem happens and write the answer down below the
problem.
3.If the answer you just provided doesn’t identify the root cause of the
problem that you wrote down in Step 1, ask Why again and write that
answer down.
4.Loop back to step 3 until the team is in agreement that the problem’s root
cause is identified. Again, this may take fewer or more times than five
Whys.
A key phrase to keep in mind in any 5 Why exercise is
"people do not fail, processes do".

4. 5 Whys Worksheet
Define the Problem:
Why is
that?
2.
1.
3.
4.
5.
Action:
Why is
that?
Why is
that?
Why is
that?
Caution:
- If your last answer is
something you can’t
control, go back up to the
previous answer
- Cannot because of a
person

5. 5 Whys Examples
Problem Statement: Customers are unhappy because they are being shipped products that
don’t meet their specifications.
1. Why are customers being shipped bad products?
- Because manufacturing built the products to a specification that is different from what the
customer and the sales person agreed to.
2. Why did manufacturing build the products to a different specification than that of sales?
- Because the sales person expedites work on the shop floor by calling the head of
manufacturing directly to begin work. An error happened when the specifications were being
communicated or written down.
3. Why does the sales person call the head of manufacturing directly to start work instead of
following the procedure established in the company?
- Because the “start work” form requires the sales director’s approval before work can begin
and slows the manufacturing process (or stops it when the director is out of the office).
4. Why does the form contain an approval for the sales director?
- Because the sales director needs to be continually updated on sales for discussions with
the CEO.
In this case only four Whys were required to find out that a non-value added signature
authority is helping to cause a process breakdown.

6. 5 Whys – Our Case Study
Problem Statement: Astrios laser engine power dropped or changed during alignment or
testing.
1. Why did the Astrios power drop?
- Because the input end of the test fiber with the Astrios burned.
2. Why did the fiber input end burn?
- Because the laser power came out of coupler higher than 15mW while aligning or peaking
up the laser beam with the fiber.
3. Why did the laser power come out more than 15mW?
- Because an ND filter was needed but was not put to reduce the power in 405nm laser path
before the coupler.
4. Why was an ND filter needed but not put in the laser path?
- Because there was no other way to control the laser power and there no warning sign or
instruction to remind the technician to put an ND filter around the workstation.
5. Why wasn’t an instruction and warning sign available around the workstation?
- Because the work instruction is not easy to access and the Traveler don’t have the
warning words to remind the technicians.
Action: ?

7. Phenomenon
(Issue)
Phenomenon 1 Phenomenon 2
(Symptom 1)
Phenomenon 3
(Symptom 2)
Phenomenon 4
(Symptom 3)
…
Symptom
(Problem)
Symptom 1 Symptom 2
(Cause 1)
Symptom 3 Symptom 4 …
Cause
(Why)
Cause 1
(Why)
Cause 2
(Why)
Cause 3
(Why)
Cause 4
(Why)
…
Action
Action 1 Action 2 Action 3 Action 4 …
5 Whys – Robert Xiong’s Approach

8. 5 Whys – Our Case Study
Phenomenon
(Issue)
ILE power dropped or
changed during
alignment or testing.
The output end of the
fiber with the ILE
burned.
There were dusts on
the fiber output end.
The adapter
connected to the fiber
end for power
measurement was
dirty with dusts.
There are dusts
around the
workstations.
Symptom
(Problem)
The output end of the
fiber with the ILE
burned.
There were dusts on
the fiber output end.
The adapter
connected to the fiber
end for power
measurement was
dirty with dusts.
There are dusts
around the
workstations.
The whole production
area is open and no
dust control is
required.
Cause
(Why)
There were dusts on the
fiber output end.
The adapter
connected to the fiber
end for power
measurement was
dirty with dusts.
There are dusts
around the
workstations.
The whole production
area is open and no
dust control is
required.
1. Not that severe
before?
2. Cost?
3. Budget?
Action
Clean and check the
fiber ends before
alignment or testing.
Clean the adapter
before connecting the
fiber end to it.
Clean the
workstations daily.
Make proper dust
control/clean room
criteria for the
production.
…

9. Take-away Quotation
“If you don’t ask the right questions, you don’t get
the right answers. A question asked in the right way
often points to its own answer. Asking questions is
the ABC of diagnosis. Only the inquiring mind
solves problems.”
– Edward Hodnett

10. Question?