Ishikawa Diagram, also known as the
Fishbone Diagram or
is a tool used for systematically identifying and presenting all the
possible causes of a particular problem
in graphical format. The possible causes are presented at various
levels of detail in connected branches, with the level of detail
increasing as the branch goes outward, i.e., an outer branch is a cause
of the inner branch it is attached to. Thus, the outermost
branches usually indicate the root causes of the problem.
Diagram resembles a
alternative name "Fishbone Diagram") - it has a box (the 'fish head')
that contains the statement of the problem at one end of the diagram.
From this box originates the main branch (the 'fish spine') of the
diagram. Sticking out of this main branch are major branches that
categorize the causes according to their nature.
semiconductor manufacturing, 4 major branches are often used by
beginners, referred to as the
'4 M's', corresponding to 'Man',
'Machine', 'Materials', and 'Methods'. Sometimes 5 branches are used
('5 M's'), with the fifth branch standing for 'Measurement', or even
'M-vironment.' These 'M's' or problem cause categories are
used to classify each cause identified for easier analysis of data. Of course, one is not
constrained to use these categories in a fishbone diagram.
Experienced users of the diagram add more branches and/or use different categories, depending
on what would be more effective in dealing with the problem. Figure 1
of an Ishikawa Diagram.
The Basic '4 M's' Framework of an Ishikawa Diagram
The Ishikawa Diagram is
employed by a problem-solving team as a tool for
inputs (as to what are the causes of the problem they're addressing) systematically and graphically,
with the inputs usually coming from a brainstorming session. It
enables the team to
the problem occurs, and not on the history or symptoms of the problem,
or other topics that digress from the intent of the session. It also
displays a real-time
collective inputs of the team as it is updated.
Diagram is usually constructed by the problem-solving team using the
following basic steps:
prepare the basic framework of the Ishikawa Diagram on a large
writing area, such as a whiteboard or a flipchart;
2) define the problem
that needs to be addressed and describe it in clear and specific terms,
then write this description in the problem box or fish head of the
3) finalize the cause
categories of the major branches and write these at the tips of the
major branches; if the members are all new to the Ishikawa Diagram and
can't decide on which categories to write, use the 4 M's as categories;
using these basic brainstorming guidelines:
participant will be asked one at a time to give a cause of the problem
(only one input per turn!), saying 'Pass' if he or she can't think of
any during his or her turn;
b) each cause
identified will be 'hung' on the major branch of the category it belongs
to; if it's the cause of another cause that's already on the diagram,
then it must be 'hung' on the branch of the latter; if applicable, a
cause may be placed on several branches;
brainstorming session will continue until everyone says 'Pass'.
the Ishikawa Diagram once it's finished.
many ways to interpret the Ishikawa Diagram. The fastest and
simplest way to do it is for the group to choose the top five causes on
the diagram and rank them, using their collective knowledge and any data
available. The selection of the major causes may be done by voting
or any other process that allows the group to agree on the ranking.
The selected causes are then encircled on the diagram, with their ranks
written beside them. The team may then investigate these causes
further and use problem-solving techniques to eliminate their
Example of a simple but finished Ishikawa Diagram
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