Dr. Kaoru Ishikawa, a Japanese quality control statistician,
has invented the fishbone diagram. Hence, it is also referred as an Ishikawa
diagram. Its analyses provide a systematic way of looking at effects and the
causes that create or contribute to those effects. It looks like a fish
skeleton when it is depicted which is why it is known as a Fish bone diagram.
Let us understand how it looks before we take a scenario and try to explain the
As shown in the figure, the causes (Cause1, Cause2, Cause3
and Cause4) for the Effect have been shown. We use Fishbone diagrams for some
of thes reasons stated below.
To study a problem/issue to determine the root cause.
To study all the possible reasons why a process is having difficulties
Identifying the areas for data collection.
To study why a process is not performing properly or producing
the desired results.
Let us now take a real time scenario and try to understand it.
Scenario – Schedule Variance of the Project life cycle is
Factors – One of the major factors that lead to the schedule
variance is insufficient requirements Analysis. Due to this, the design phase
has gotten delayed and also effected, coding phase is also effected, the
testing delayed, etc. Here, our problem or effect that we are currently
discussing is about the schedule variance of the entire project and not a
particular phase. Hence, we take into account all the factors (even if they are
interdependent on each other).
Figure 3 shows a fishbone diagram explaining the problem
“Schedule Variance.” One of the main causes shown in the figure is
“Insufficient Requirements.” These can have sub-cause(s) like unrealistic
project plan, which leads to insufficient requirements. Lack of domain
knowledge can lead to insufficient requirements. Delay of requirements [Lack of
requirements document] has led to delay in design phase. The lack of design
documents leads to delay in the coding. Lack of motivation can lead to
attrition rate of man power. All these causes have led to the schedule variance
of the project up to 30%.