Cause and Effect Diagram

1
Cause and Effect Diagram
CA/PA-RCA Basic Tool

• Sector Enterprise Quality Quality and Mission
  Assurance
• Northrop Grumman Corporation
• Integrated Systems

2
What is Cause and Effect Analysis

• Cause and Effect Analysis is a technique for
  identifying all the possible causes (inputs)
  associated with a particular problem / effect
  (output) before narrowing down to the small
  number of main, root causes which need to be
  addressed.

3
Why use Cause and Effect Analysis

• Cause and Effect Analysis is a valuable tool for
• Focusing on causes not symptoms capturing the
  collective knowledge and experience of a
  group
• Providing a picture of why an effect is
  happening
• Establishing a sound basis for further data
  gathering and action
• Cause and Effect Analysis can also be used to
  identify all of the areas that need to be
  tackled to generate a positive effect.

4
What is a Cause and Effect Diagram

• A Cause and Effect diagram (also known as a
  Fishbone or Ishikawa diagram) graphically
  illustrates the results of the analysis and is
  constructed in steps. Cause and Effect Analysis
  is usually carried out by a group who all have
  experience and knowledge of the cause to be
  analyzed.
• Cause-and-Effect diagrams graphically display
  potential causes of a problem
• The layout shows Cause-and-Effect relationships
  between the potential causes

5
Why use a Cause and Effect Diagram

• It is common for people working on improvement
  efforts to jump to conclusions without studying
  the causes, target one possible cause while
  ignoring others, and take actions aimed at
  surface symptoms
• Cause-and-effect diagrams are designed to
• Stimulating thinking during a brainstorm of
  potential causes
• Providing a structure to understand the
  relationships between many possible causes of a
  problem
• Giving people a framework for planning what data
  to collect
• Serving as a visual display of causes that have
  been studied
• Helping team members communicate within the team
  and with the rest of the organization

6
How do I do it?

• 1. Identify the Problem/Issue
• Select a particular problem, issue or effect.
• Make sure the problem is specific, tightly
  defined and relatively small in scope and that
  everyone participating understands exactly
  what is being analyzed.
• Write the problem definition at the top of the
  flip chart or whiteboard.

7
How do I do it? (continued)

• 2. Brainstorm
• Conduct a Brainstorm of all the possible causes
  of the effect, i.e., problem.
• Have a mixed team from different parts of the
  process (e.g., assemblers and testers).
• Get a fresh pair of eyes - from someone who is
  not too close to the process.
• Have a facilitator - an impartial referee.
• Everyone is an equal contributor (leave stripes
  at the door).
• Fast and furious - go for quantity rather than
  quality (of ideas) at first.
• Involve everyone, or question why he/she is here.
• Timing - set an upper limit and best time/day of
  the week.
• Offer an incentive (free lunch?).
• Know when to stop.
• Recognize that this is a snapshot of how the
  group thinks today.
• Re-visit the problem again.
• Refer also to the Process Mapping tool.
• Consider (how) should you involve your customer?

8
How do I do it? (continued)

• 2. Brainstorm (continued)
• Write each idea on a Post-It to make it easy to
  transfer them onto the fishbone diagram later. Be
  careful not to muddle causes and solutions at
  this stage.
• It is important to brainstorm before identifying
  cause categories otherwise you can constrain the
  range of ideas. However, if ideas are slow in
  coming use questions such as, what about?, to
  prompt thoughts.

9
How do I do it? (continued)

• 3. Draw fishbone diagram
• Place the effect at the head of the fish
• Include the 6 recommended categories shown below

10
How do I do it? (continued)

• 4. Align Outputs with Cause Categories
• Review your brainstorm outputs and align with the
  recommended major cause categories, e.g., the
  People, Method, Machine, Material, Environment
  and Measurement System. NoteThese may not fit
  every situation and different major categories
  might well be appropriate in some instances,
  however, the total should not exceed six. Other
  categories may include Communications, Policies,
  Customer/Supplier Issues etc.

Tip ! The 6 categories recommended will address
almost all scenarios. However, there is no one
perfect set of categories. You may need to adapt
to suit the issue being analyzed.
11
How do I do it? (continued)

• 5. Allocate Causes
• Transfer the potential causes from the brainstorm
  to the diagram, placing each cause under the
  appropriate category.
• If causes seem to fit more than one category then
  it is acceptable to duplicate them. However, if
  this happens repeatedly it may be a clue that the
  categories are wrong and you should go back to
  step 4.
• Related causes are plotted as twigs on the
  branches. Branches and twigs can be further
  developed by asking questions such as what?,
  why? how?, where? This avoids using broad
  statements that may in themselves be effects.
  Beware, however, of digging in and getting into
  bigger issues that are completely beyond the
  influence of the team.

12
How do I do it? (continued)

• 6. Analyze for Root Causes
• Consider which are the most likely root causes of
  the effect. This can be done in several ways
• Through open discussion among participants,
  sharing views and experiences. This can be
  speeded up by using Consensus Decision Making.
• By looking for repeated causes or number of
  causes related to a particular category.
• By data gathering using Check Sheets, Process
  Maps, or customer surveys to test relative
  strengths through Pareto Analysis.
• Once a relatively small number of main causes
  have been agreed upon, Paired Comparisons, can
  be used to narrow down further.
• Some groups find it helpful to consider only
  those causes they can influence.

13
How do I do it? (continued)

• 7. Test for Reality
• Test the most likely causes by, e.g., data
  gathering and observation if this has not already
  been done.
• The diagram can be posted on a wall and added to
  / modified as further ideas are generated either
  by the team or by others who can review the
  teams' work.
• Cause and Effect Analysis can be combined with
  Process Mapping.
• A fishbone may be developed for each discrete
  activity within the process that is generating
  the output / effect so that causes are linked to
  particular steps in the process.

14
Sources of Variation - People

• The activities of the workers.
• Variations caused by skill, knowledge,
  competency and attitude

• Types of Questions that may be Asked Note, this
  is not a definitive list of questions that may be
  asked to identify potential source of variation
• Does the person have adequate supervision and
  support?
• Does the person know what he is expected to do
  in his job?
• How much experience does the person have?
• Does the person have the proper motivation to do
  his best work?
• Is the person satisfied or dissatisfied with his
  job?
• Is the person more- or less-productive at
  certain times of the day?
• Do physical conditions such as light or
  temperature affect their work?
• Does the person have the tools/equipment needed
  to do the job?
• Who does the person contact when problems arise?
• Is the work load reasonable?

15
Sources of Variation - Method

• The methods used to produce the products.
• Variations caused by inappropriate methods or
  processes.

• Types of Questions that may be Asked Note, this
  is not a definitive list of questions that may be
  asked to identify potential source of variation
• How is the method used defined?
• Is the method regularly reviewed for adequacy?
• Is the method used affected by external factors?
• Have other methods been considered?
• How does the operator know if the method is
  operating effectively?
• Is statistical analysis used to verify the
  effectiveness of the method?
• What adjustments must the operator make during
  the process?
• Have any changes been made recently in the
  process?

16
Sources of Variation - Machine

• The equipment used to produce the products.
• Variations caused by temperature, tool wear and
  vibration.

• Types of Questions that may be Asked Note, this
  is not a definitive list of questions that may be
  asked to identify potential source of variation
• How old is the equipment or machinery?
• Is it maintained regularly?
• Is the machine affected by heat or vibration or
  other physical factors?
• How does the operator know if the machine is
  operating correctly?
• Is statistical analysis used to verify the
  capability of the machine?
• What adjustments must the operator make during
  the process?
• Have any changes been made recently in the
  process?

17
Sources of Variation - Material

• The "ingredients" of a process.
• Variations caused by materials that differ by
  industry, product and stage of production.

• Types of Questions that may be Asked Note, this
  is not a definitive list of questions that may be
  asked to identify potential source of variation
• How is the material produced?
• How is the material verified?
• How old is the material?
• How is quality judged prior to your operation?
• What is the level of quality?
• How is the material packaged?
• Can temperature, light or humidity affect the
  material quality?
• Who is the material supplier?
• Has there been a change in suppliers?

18
Sources of Variation - Environment

• The methods used to control the environment.
• Variations caused by temperature changes,
  humidity etc.

• Types of Questions that may be Asked Note, this
  is not a definitive list of questions that may be
  asked to identify potential source of variation
• How are environmental conditions monitored?
• How are environmental conditions controlled?
• How is the environment control measuring
  equipment calibrated?
• Are there changes in conditions at different
  times of the day?
• How does environmental change impact the
  processes being used?
• How does environmental change impact the
  materials being used?

19
Sources of Variation Measurement System

• The methods and instruments used to evaluate
  products.
• Variations caused by measuring techniques, or
  calibration and maintenance of the
  instruments.

• Types of Questions that may be Asked Note, this
  is not a definitive list of questions that may be
  asked to identify potential source of variation
• How frequently are products inspected?
• How is the measuring equipment calibrated?
• Are all products measured using the same tools
  or equipment?
• How are inspection results recorded?
• Do inspectors follow the same procedures? (Is
  there a set of standards?)
• Do inspectors know how to use the test equipment?

20
Example (showing 4 of the 6 recommended
categories)
21
Cause and Effect Diagram
Questions?
Call or e-mail Bob Ollerton 310-332-1972/310-3
50-9121 robert.ollerton_at_ngc.com