Ishikawa Diagrams
Ishikawa diagrams are named after their inventor, Kaoru Ishikawa. They are also called fishbone
charts, after their appearance, or cause and effect diagrams after their function. Their function is
to identify the factors that are causing an undesired effect (e.g., defects) for improvement action,
or to identify the factors needed to bring about a desired result (e.g., a winning proposal). The
factors are identified by people familiar with the process involved. As a starting point, major
factors could be designated using the "four M's": Method, Manpower, Material, and Machinery; or
the "four P's": Policies, Procedures, People, and Plant. Factors can be subdivided, if useful, and
the identification of significant factors is often a prelude to the statistical design of experiments.
Figure 3 is a partially completed Ishikawa diagram attempting to identify potential causes of
defects in a wave solder process