A why-why diagram is used to identify the root causes of a problem when there are multiple factors to consider. There may be multiple answers at each stage, and each of these answers need to go through a separate process of the why-whys analysis. It is an extension of the 5 Whys approach where they are similar in that they both ask the same Why question multiple times. #WhyWhyDiagram

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Why-Why Diagram
Beyond the Five Whys: Exploring the Hierarchical Causes with the Why-Why Diagram
WHY?
WHY?

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Introduction
5 Whys is most effective when used to solve simple problems with a single
root cause.
Why-Why Diagram 2
PROBLEM
ROOT
CAUSE
It follows a path that is linear toward the root cause.

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Introduction
Oftentimes, a problem is the result of multiple causes occurring together.
Why-Why Diagram 3
PROBLEM
Each cause is the result of a further cause or multiple causes.

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Introduction
For example, leaks in a house could be due to several underlying issues . . .
Why-Why Diagram 4
Faulty seals
Damaged plumbing fixtures
Corrosion in metal plumbing pipes
Cracked tiles or grout
Poorly installed fixtures
Each of the above causes is the result of a further cause or multiple causes.

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Introduction
Each time you ask why, there might be more
than one answer for each why.
Why-Why Diagram 5
In other words, a problem may have
different potential root causes, not
only one!

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Definition
A Why-Why Diagram is used to identify the root causes of a problem when
there are multiple factors to consider.
Why-Why Diagram 6
There may be multiple answers at each
stage, and each of these answers need
to go through a separate process of
the why-whys analysis.
The result can be represented in a hierarchical tree format

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Definition
It is an extension of the 5 Whys approach.
Why-Why Diagram 7
Why?
Why?
Why? Why?
Why?
Both technique are similar in that they
both ask the same Why question
multiple times.

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Benefits
Why-Why Diagram 8
Identifies the potential factors that
may cause an effect to prevent future
problems.
Identifies the potential causes of an
undesirable effect in order to solve it.
Provides useful information for later
problem-solving analyses.

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Structure
Such hierarchical structure of potential causes can be represented in a tree
diagram or a fishbone diagram.
Why-Why Diagram 9
The information in this diagram is in fact the same as what you would find in a
fishbone diagram.

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Structure
The problem will normally be placed on the left side of the diagram
whereas the most specific causes will be placed on the right side.
Why-Why Diagram 10
Lines are used to
connect related series
of causes
Problem
Possible
cause
Possible
cause
Possible
cause
Possible
cause
Possible
cause
Possible
cause
Possible
cause

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Structure
Why-Why Diagram 11
Problem
Possible
cause
Possible
cause
Possible
cause Possible
cause
Possible
cause
Possible
cause
Possible
cause
Possible
cause
Possible
cause
Possible
cause
Possible
cause
Possible
cause
Possible
cause
Root
cause
Possible
cause
Possible
cause
Root
cause
Possible
cause
Root
cause
Root
cause
Root
cause
Root
cause
Root
cause
Root
cause
Level #1 Level #2 Level #3 Level #4 Level #5
Levels of Whys
The most specific causes will be reflected as you move toward the right.

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Structure
Potential causes can be organized into categories to provide better focus
and easier reference.
Why-Why Diagram 12
Invoice faults
Measurement
Environment
Equipment
Man
Method
Material
Inadequate printers
System not integrated
Poor technical support
Increased workload
Manual data entry
Poor audit system
Poor ergonomics
Noisy office
Inadequate paper supply
Measurement variability
Difficult process
Cause categories using the 6 Ms approach

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Steps for Drawing the Why-Why Diagram
Often constructed during team brainstorming sessions.
Why-Why Diagram 13
By going through the steps of drawing the diagram with your team, everyone gains a
better understanding of the problem, making the solution easier to find later.

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Steps for Drawing the Why-Why Diagram
Why-Why Diagram 14
With your team, clearly state the problem then write it on a post-it card
• Place the problem card on the left side of a whiteboard or wall.
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Steps for Drawing the Why-Why Diagram
Why-Why Diagram 15
Ask “Why the problem occurs”?
• Let the team members write as many causes as possible on post-it cards.
• Group similar causes together, then stick them up to the right of your problem.
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Steps for Drawing the Why-Why Diagram
Why-Why Diagram 16
Ask Why again for the generated causes and write the causes to the right
• Keep asking “Why” until the team identifies the root causes of the problem.
• Take time to ensure the appropriateness of the recorded information.
• You may need to collect and analyze data to confirm identified root causes are
real.
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Steps for Drawing the Why-Why Diagram
Why-Why Diagram 17
Leave the chart on the wall for few days and update it as new potential causes become apparent
• Once you are finished, discuss and agree on the corrective actions that will
permanently solve the problem.

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Two Formats
Why-Why Diagram 18
From
center to
the outside
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From left to
right

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Example – Poor Sales
A team has created a why-why diagram to identify the underlying causes
behind the decline in sales during the last quarter.
Why-Why Diagram 19
WHY?
Poor sales
Lack of promotion
Ineffective distribution
High manufacturing
cost
Lack of marketing
strategy
Limited advertisement
budget
Small sales staff
Poor product design
Poor quality
High price
WHY?

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Example - Customer Complaints
A restaurant team has constructed a why-why diagram as part of their efforts to
resolve a complaint regarding the increased number of customer complaints about
the taste of their coffee.
Why-Why Diagram 20
Coffee not
tasting good
Unclean coffee
maker
Low water quality
Over roasting
Using water from
the tap
Long roasting
period
Coffee maker not
cleaned well
Easier to access
tap water
Cleaning SOP not
followed
Cheaper than
bottled water
Coffee maker not
cleaned daily
As per current work
instructions
No one knows
about the SOP
Cost savings
program in place
Old obsolete work
practices
Can’t change
current machine
settings
Cost savings is a
top priority
SOP is not shared
yet
No system to
update work
instructions
Manual doesn't
cover changing the
settings
Current machine
settings
No cleaning
schedule in place

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Further Information
Be aware of adding causes which are actually solutions.
Why-Why Diagram 21
The main idea behind the why-why diagram is to brainstorm all possible causes that
may contribute to a problem, and not brainstorm solutions.

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Further Information
A cause-and-effect matrix can be used to prioritize the causes of the
problem.
Why-Why Diagram 22
Prioritizing and selecting the key causes will minimizes the need for more statistical
analysis of inputs that are unlikely to have an impact on the output.

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