Cause & Effect
The cause & effect diagram is the brainchild of Kaoru
Ishikawa, who pioneered quality management processes in the
Kawasaki shipyards, and in the process became one of the founding
fathers of modern management. The cause and effect diagram is
used to explore all the potential or real causes (or inputs) that
result in a single effect (or output). Causes are arranged
according to their level of importance or detail, resulting in a
depiction of relationships and hierarchy of events. This can help
you search for root causes, identify areas where there may be
problems, and compare the relative importance of different
Causes in a cause & effect diagram are frequently arranged
into four major categories. While these categories can be
anything, you will often see:
- manpower, methods, materials, and machinery (recommended for
- equipment, policies, procedures, and people (recommended for
administration and service).
These guidelines can be helpful but should not be used if they
limit the diagram or are inappropriate. The categories you use
should suit your needs. At SkyMark, we often create the branches
of the cause and effect tree from the titles of the affinity sets
in a preceding affinity diagram.
The C&E diagram is also known as the fishbone diagram
because it was drawn to resemble the skeleton of a fish, with the
main causal categories drawn as "bones" attached to the spine of
the fish, as shown below.
Cause & effect diagrams can also be drawn as tree
diagrams, resembling a tree turned on its side. From a single
outcome or trunk, branches extend that represent major categories
of inputs or causes that create that single outcome. These large
branches then lead to smaller and smaller branches of causes all
the way down to twigs at the ends. The tree structure has an
advantage over the fishbone-style diagram. As a fishbone diagram
becomes more and more complex, it becomes difficult to find and
compare items that are the same distance from the effect because
they are dispersed over the diagram. With the tree structure, all
items on the same causal level are aligned vertically.
To successfully build a cause and effect diagram:
- Be sure everyone agrees on the effect or problem statement
- Be succinct.
- For each node, think what could be its causes. Add them to
- Pursue each line of causality back to its root cause.
- Consider grafting relatively empty branches onto others.
- Consider splitting up overcrowded branches.
- Consider which root causes are most likely to merit further
Other uses for the Cause and Effect tool include the
organization diagramming, parts hierarchies, project planning,
tree diagrams, and the 5 Why's.
Create Cause and Effect Diagrams with PathMaker.