Cause and Effect Analysis: 1. Fishbone Diagram 2. Cause and Effect Matrix

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Cause and Effect Analysis1. Fishbone
Diagram2. Cause and Effect Matrix
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Learning Objectives

• Define the relationship between Cause and Effect
• Explain use and construction of
• Fishbone Diagram
• Guidelines for Brainstorming
• Cause and Effect Matrix
• Learn how to integrate Fishbone Diagram and Cause
  Effect Matrix into your Company SOPs

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What do you mean by Cause Effect?
A PROBLEM WHICH HAS OCCURED
A POTENTIAL FUTURE PROBLEM
(FMEA)
EFFECT Symptoms that provide evidence of the
problem
EFFECT Symptoms that would result from the
problem
CAUSE Events/conditions that led to the problem
CAUSE Events/conditions that would lead to the
problem
Dave Wessel, An Ounce of Prevention, Quality
Progress, Dec, 1998
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Cause - Effect Relationship
CAUSE Events/conditions that led to the problem
Dave Wessel, An Ounce of Prevention, Quality
Progress, Dec, 1998
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Fishbone Diagram
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What is a Fishbone Diagram?

• A visual tool used to identify, explore and
  graphically display all the possible causes
  related to a problem to discover root causes.
• A Fishbone diagram is also known as a Cause and
  Effect Diagram or Ishikawa Diagram.

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Dr Kaoru Ishikawa

• Quality control statistician
• Professor in University of Tokyo
• One of the pioneers of Japans quality revolution
  in the 1940s
• Played major role in growth of QC circles
• Best known for formalizing use of
  Cause-and-Effect Diagram
• Won the Deming Prize and Shewhart Medal
• ASQ established the Ishikawa Medal to recognize
  the human side of quality

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Why Use Fishbone Diagrams?

• To discover the most probable causes to a problem
  (or effect)
• Sometimes, the effect can be a desirable effect.
• When something desirable has happened, it is
  useful to find out what caused it so that you can
  make it happen again
• To visual possible relationships between causes
  for a given problem under investigation

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Constructing a Fishbone Diagram

• Establish what the problem (effect) is
• It must be stated in clear and concise terms,
  agreed by everyone.
• Write the effect on the head of the fish
• Decide the major categories of causes
• Brainstorming
• Use standard categories such as 5ME (Machines,
  Materials, Methods, Manpower, Measurement
  Environment)
• Use major steps in the process if the effect is
  resulted from a recognizable process
• See example????

Lets create a Fishbone Diagram using Minitab
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Constructing a Fishbone Diagram
Stat ðQuality Tools ðCause-and-Effect
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Constructing a Fishbone Diagram
Fishbone Diagram for Surface Flaws
List specific causes in each category
Man
Materials
Measurements
Surface Flaws
Problem (effect) at the head of the fish
Machines
Methods
Environment
Major categories of causes (or sometimes call
major bones)
Why do we need to group the causes?
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Constructing a Fishbone Diagram

• 4. Identify possible causes through
  Brainstorming
• Identify specific causes within each major
  category that may be affecting the problem.

Fishbone Diagram for Surface Flaws
Personnel
Materials
Measurements
3. Continue asking Why is this happening?
until you no longer get useful information.
2. Repeat this procedure with each specific cause
to produce sub-causes.
Micrometers
Calibration Method
Alloys
Shifts
Calibration Interval
Precision
Accuracy
Lubricants
Supervisors
Microscopes
Suppliers
Training
Operators
Inspectors
Surface Flaws
Machine feedrate
Speed
Machine rpm
Brake
Lathes
Brand of bit
Condensation
Engager
Bits
Size of bit
1. The team should ask What are the machine
issues affecting/causing the problem?
Moisture
Angle
Sockets
Machines
Methods
Environment
When do we know we have reached the root cause ?
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Analyzing a Fishbone Diagram

• 5. When brainstorming session is completed,
  every cause should be labeled as either a C,
  N or X.
• C variables that must be held as constant as
  possible and require standard operating
  procedures to insure consistency
• N variables that are noise or uncontrolled
  variables and cannot be cheaply/easily held
  constant
• X variables considered to be KPIVs and need to
  be experimented to determine what influence each
  has on the output and what their optimal
  settings should be to achieve customer-desired
  performance

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Analyzing a Fishbone Diagram

• 6. The team should analyze and zoom in those
  most likely causes.
• Helpful Hint
• Look out for causes that appear in more than one
  category. They may be the most likely causes.
• 7. The most likely causes should be prioritized
  for further investigation.

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Integrating Fishbone Diagram into SOPs
Example of how fishbone diagram can be used in
SCAR.
Section of SCAR Procedure
Received complaint/reject from customer, in-house
or supplier.
Generate report for management review
Fishbone diagram can be used here to brainstorm/
identify root causes
QA personnel verify the defects.
Follow up on CAR
Issue CAR to production.
-receive CAR reply from production - reply to
customer
Purge in-house stock
Hold meeting with relevant departments (if
necessary)

1. Fishbone diagram can be used here to brainstorm/
   identify root causes.
2. To prioritize and work on most likely causes.

Should also update Fishbone diagram
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Integrating Fishbone Diagram into SOPs
Example of how fishbone diagram can be used in
SPC control
Section of SPC Control Procedure
Fishbone diagram can be used here to brainstorm/
identify root causes
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Link Tools Integration Tasks to Work Breakdown
Structure

• The effort to integrate Fishbone Diagram into SPC
  and SCAR procedures should be translated into
  specific tasks in the Work Breakdown Structure.

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Cause Effect Matrix
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Cause and Effect Matrix
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Description Cause and Effects Matrix

• Simple QFD (Quality Function Deployment) matrix.
• Used to relate and prioritize Xs to customer Ys
  through numerical ranking using the process map
  as the primary source.
• Ys are scored as importance to the customer
• Xs are scored as to relationship to outputs
• This is the teams first stab at determining Y
  f(X)

• Results
• Pareto of Key Inputs to evaluate in the FMEA and
  Control Plans
• Input into the Capability Study
• Input into the initial evaluation of the Process
  Control Plan

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Constructing a Cause Effect Matrix
1. List key outputs (Ys)
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Constructing a Cause Effect Matrix
2. Rank Ys with respect to customer importance
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Constructing a Cause Effect Matrix
3. List key inputs (Xs)
Input Variables
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Constructing a Cause Effect Matrix

• You are ready to correlate customer requirements
  to the process input variables
• Avoid confusion and inconsistency by establishing
  scoring criteria
• 0 no correlation
• 1 the process effect only remotely affects the
  customer requirement
• 4 The input variable has a moderate effect on
  the customer requirement
• 9 The input variable has a direct and strong
  effect on the customer requirements

Note Not recommended to use more than 5
different criteria.
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Constructing a Cause Effect Matrix
4. Relate Xs to Ys
Xs
Ys
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Constructing a Cause Effect Matrix
5. Cross-multiply and add
Key inputs are now ranked in importance with
respect to the key outputs
So??
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How Cause Effect can Fit into Process
Improvement Activities
CE Matrix
The Big Picture
Outputs
Inputs
Capability Summary
Control Plan Summary
FMEA
The Key Outputs are evaluated ability to meet
customer spec.
The Key Inputs are evaluated for process control
Key Inputs are explored while evaluating process
for potential failure
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Integrating Cause Effect Matrix into SOPs
Example of how Cause and Effect Matrix can be
used in SCAR.
Section of SCAR Procedure
Received complaint/reject from customer, in-house
or supplier.
Generate report for management review
Cause and Effect Matrix can be used in
conjunction with fishbone diagram to identify,
rank and prioritize the key causes.
QA personnel verify the defects.
Follow up on CAR
Issue CAR to production.
-receive CAR reply from production - reply to
customer
Purge in-house stock
Hold meeting with relevant departments (if
necessary)
Cause and Effect Matrix can be used in
conjunction with fishbone diagram to identify,
rank and prioritize the key causes.
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Integrating Cause Effect Matrix into SOPs
Example of how Cause Effect Matrix can be used
in SPC control
Section of SPC Control Procedure
Cause and Effect Matrix can be used in
conjunction with fishbone diagram to identify,
rank and prioritize the key causes.
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Link Tools Integration Tasks to Work Breakdown
Structure

• The effort to integrate Cause Effect Matrix
  into SPC and SCAR procedures should be translated
  into specific tasks in the Work Breakdown
  Structure.

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End of TopicAny question?
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Product/Manufacturing Example
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Transactional Example
Estimated Ship Date Change - CAUSE EFFECT /
FISHBONE
WCSC PRACTICES
MDC CAPACITY
MDC PRACTICES
SCHEDULE CHANGES
- Unrealistic Del. Req Dates -
Customer Order Priority Changes
- B.O.. Consol. - SC late
- Firm - Planned
- Receiving - Picking - PC delays - Off
shift support
ORDER CANCELLATION
Estimated Ship Date Changes
- Bad IT days - Table Maint.
- Waiting for Delivery Appt.
PLANNED SHIP DATE ALGORITHM
- No Delivery Constraints
After initial PSD - Back Ord. Release
Logic - Cust Priority vs. availability
-Future orders at AP
- Availability Overrides - No Stocks
IN TRANSIT TIMES
- Late PT print - Late EDI data
ESD ALGORITHM ANOMALIES
APPOINTMENT CUSTOMER
INVENTORY ACCURACY
LDSS
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A technique to generate a large number of ideas
or possibilities in a relatively short time frame.
Brainstorming
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• Why Use Brainstorming?
• A tool for the Team (not individual)
• A method to generate a lot of ideas
• Two persons knowledge and ideas are
• always more than an individuals
• Input for other CE tools
• Active participation

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How to Conduct a Brainstorming Session

• Team Makeup
• Experts
• Semi experts
• Implementers
• Analysts
• Technical staff who will run the experiment
• Operators
• Discussion Rules
• Suspend judgement
• Strive for quantity
• Generate wild ideas
• Build on the ideas of others
• Leaders rules for Brainstorming
• Be enthusiastic
• Capture all the ideas
• Make sure you have a good skills mix
• Push for quantity
• Strictly enforce the rules

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Root Cause

• How do we know when we have reached
• ROOT CAUSE ?
• Root Cause is the lowest cause in a chain of
  cause and effect at which we have some capability
  to cause the break
• Its within our capability to unilaterally
  control, or to influence, changes to the cause

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Span of Control / Sphere of Influence
Before we begin, we must establish the context in
which the Cause-Effect will be used.
Span of Control - areas where we have a high
degree of control over parts or functions,
virtually complete authority to change
anything Sphere of Influence - areas where we
can influence things to varying degrees but dont
have direct control. Outside Environment - where
we have neither control nor influence
OUTSIDE, UNCONTROLLED ENVIRONMENT
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Points to Note for Fishbone Diagram

• Treat the cause-and-effect diagram as a living
  document
• As new variables are discovered, update the
  cause-and-effect diagram
• After your experimental investigations, when you
  have optimized the X factors, and implemented
  control, update them to C.
• Therefore, ideally, when the fishbone diagram has
  more Cs, the better we can control the effect
  and improve its performance measure.