Continuous Improvement Toolkit
Why-Why Diagram
WHY?
WHY?
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Why-Why Diagram
5 Whys is most effective when used to solve simple
problems with a single root cause
ROOT
PROBLEM
CAUSE
It follows a path that is linear toward the root cause
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Why-Why Diagram
Oftentimes, a problem is the result of multiple causes
occurring together
PROBLEM
Each cause is the result of a further cause or multiple causes
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Why-Why Diagram
Each time you ask why, there might be more than one answer
In other words, a problem may have different potential root causes
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Why-Why Diagram
A Why-Why Diagram is an extension of the 5 Whys approach
WHY?
WHY? WHY? WHY?
WHY?
They are similar in that they both ask the same Why question multiple times
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Why-Why Diagram
A Why-Why Diagram is used to identify the root causes of a
problem when there are multiple factors to consider
WHY?
WHY?
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
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Why-Why Diagram
Such hierarchical structure of potential causes can be
represented in a tree diagram or a fishbone diagram
The information in this diagram is in fact the same as what you would find
in a fishbone diagram, but the format is different
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Why-Why Diagram
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
Possible
Possible cause
cause
Possible Lines can be
Possible cause
used to connect
Problem cause related series of
Possible
cause causes
Possible
cause Possible
cause
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Why-Why Diagram
Levels of Whys Level #1 Level #2 Level #3 Level #2 Level #3
Possible Possible Root
cause cause cause
Possible
Possible cause Possible Root
cause cause Root
cause cause
Possible Possible Possible
cause cause cause
Root
Possible cause
Problem cause Possible
Possible
cause
Root
cause
cause
Root
Possible Root cause
Possible Possible cause cause
cause cause
Possible Possible Root
cause cause cause
The most specific causes will be reflected as you move toward the right
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Why-Why Diagram
Potential causes can be organized into categories to provide better
focus and easier reference
Cause categories using the 6 Ms approach Difficult process
Manual data entry
Method
Inadequate printers
Equipment System not integrated
Poor technical support
Invoice faults Man Increased workload
Measurement variability
Measurement
Poor audit system
Environment Poor ergonomics
Noisy office
Material
Inadequate paper supply
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Why-Why Diagram
Benefits
Identifies the potential
Identifies the potential Provides useful
factors that may cause an
causes of an undesirable information to later
effect to prevent future
effect in order to solve it problem-solving tools
problems
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Why-Why Diagram
Often constructed during team brainstorming sessions
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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Why-Why Diagram
How to Construct the Diagram
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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Why-Why Diagram
How to Construct the Diagram
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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Why-Why Diagram
How to Construct the Diagram
Ask Why again for the generated causes and write the causes to
the right
Start with the main causes and then the secondary causes and so on
//
// //
// //
//
//
// //
// //
//
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Why-Why Diagram
How to Construct the Diagram
Keep asking Why until the team identifies the root causes of the
problem
You may need to collect and analyze data to confirm identified root causes are real
// //
// //
// //
//
//
// //
// //
//
//
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Why-Why Diagram
How to Construct the Diagram
Once you are finished, discuss and agree on the corrective actions
that will permanently solve the problem
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Why-Why Diagram
Example – Poor Sales
WHY?
WHY?
Poor quality
Poor product design
High manufacturing
cost
High price
Poor sales
Poor economy
Inadequate
promotion Limited advertisement
budget
Ineffective distribution
Small sales staff
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Why-Why Diagram
Example - Customer complaint
Cost savings
Cheaper than Cost savings is
program in
bottled water a top priority
place
Using water from Easier to
Low water the tap access tap
water
quality
As per current No system to
Old obsolete
work update work
work practices
instructions instructions
Coffee not Long roasting
Can’t change
Over roasting period
Current Manual doesn't
tasting good machine
settings
current machine
settings
cover changing
the settings
Cleaning SOP No one knows SOP is not
Unclean coffee Coffee maker
not followed about the SOP shared yet
maker not cleaned well Coffee maker No cleaning
not cleaned schedule in
daily place
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Why-Why Diagram
An idea that
/// has been
chosen
///
///
///
/// /// A link
between
///
/// ///
causes that
are related
///
/// ///
///
An idea that
/// has not been
chosen
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Why-Why Diagram
From left ///
///
to right
/// ///
/// ///
/// ///
///
///
///
///
/// ///
From center
to the
/// /// /// /// ///
outside /// /// ///
/// ///
/// ///
///
///
/// /// ///
/// /// /// /// ///
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Why-Why Diagram
Further Information
Be aware of adding causes which are actually solutions
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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Why-Why Diagram
Further Information
A cause-and-effect matrix can be used to prioritize the
causes of the problem
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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Why-Why Diagram
Further Information
The measure of success for a fishbone diagram is the
quality of answers as well as the quantity of ideas
// //
//
// //
// //
//
//
//
Problem
//
// //
//
//
// //
//
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