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.
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.
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
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.
How do I
do it?
§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?
•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.
§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.
Note:
These 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.
Note:
These 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.
§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.
§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.
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.
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
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?)
standards?)
• Do inspectors know how to use the test equipment?
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