Problem Solving Technique - Fish Bone Diagram

There are many techniques of identifying problems. Fish Bone diagram is one of them. The fish bone digram is sometimes referred to as “The Ishikawa Diagram” developed by Professor Kaoru Ishikawa of the University of Tokyo. The main purpose of this technique is to identify and list all the possible causes of the problem at hand. This is basically a group technique, but can be applied individually also.

This process is called the Fishbone Diagram because of the unique way in which the information gathered is arranged visually. When the problem and its causes are recorded, they forms a figure resembling skeleton of a Fish. Mean one central line depicts it backbone and side line depicts fines. The problem is written down and enclosed in a circle on the right side of the sheet.  A straight line is drawn to the left and appears much line backbone of a fish. The next step is draw lines at 45 degree on the central line.

At the end of each of these stem lines listed all the causes of the problem that are brainstormed. These stem lines further may have more lines. Each line depicts a cause of the problem. The cause should be listed with the least complicated nearest the head of the fish and the most complicated.

The fishbone diagram can be brainstormed over more than one session. Ishikawa describes the process as one in which “you write your problem down on the head of the fish and then let it cook overnight.” When the technique is employed over two or more sessions, new ideas may arise from the three main effects:

(1)    There is time for the subconscious to work on the problem;

(2)    Participants are likely to be less inhibited as the authorship of particular contributions will be forgotten; and

(3)    People may become more immersed in the problem, if they think about it day and night.

When the diagram is completed, the individual or group begins to analyze. The stems and the branches to determine the real problem or problems that need to be solved. If simpler problems are examined first, they can be removed from consideration before more complicated problems are tackled. If the problem solver(s) decide that certain causes are more significant than others, these will be given more attention in the alternative generation stage of CPS.

Fishbone diagram of Problem – “Poor Sales of a New Product”

The fishbone diagram is an extremely useful technique for identifying problems for several reasons:

1. It encourages problem solvers to study all parts of a problem before making a decision.
2. It helps show the relationships between causes and the relative importance of those causes.
3. It helps start the creative process because it focuses the problem solver(s) on the problem.
4. It helps start a logical sequence for solving a problem.
5. It helps problem solvers see the total problem as opposed to focusing on a narrow part of it.
6. If offers a way to reduce the scope of the problem and solve less complex issues rather than more complex ones.
7. It helps keep people focused on the real problem rather than going off on tangents.

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Pareto Analysis (ABC Analysis)

In 1906, an Italian economist Vilfredo Pareto, observed that 80% of the land in Italy was owned by 20% of the population; he developed the principle by observing that 20% of the pea pods in his garden contained 80% of the peas.

Based on this philosophy, Business-management consultant Joseph M. Juran, define the Pareto Principle (also known as the 80-20 rule, the law of the vital few, and the principle of factor sparsity), that, for many events, roughly 80% of the effects come from 20% of the causes.

It is a common rule of thumb in business; e.g., "80% of your sales come from 20% of your clients". Mathematically, where something is shared among a sufficiently large set of participants, there must be a number k between 50 and 100 such that "k% is taken by (100 − k)% of the participants". The number k may vary from 50 (in the case of equal distribution, i.e. 100% of the population have equal shares) to nearly 100 (when a tiny number of participants account for almost all of the resource). There is nothing special about the number 80% mathematically, but many real systems have k somewhere around this region of intermediate imbalance in distribution.

In business the following trend are observed -

·         80% of your profits come from 20% of your customers

·         80% of your complaints come from 20% of your customers

·         80% of your profits come from 20% of the time you spend

·         80% of your sales come from 20% of your products

·         80% of your sales are made by 20% of your sales staff

Therefore, many businesses have an easy access to dramatic improvements in profitability by focusing on the most effective areas and eliminating, ignoring, automating, delegating or re-training the rest, as appropriate.

Pareto analysis is a statistical technique in decision making that is used for selection of a limited number of tasks that produce significant overall effect. It uses the Pareto principle – the idea that by doing 20% of work, 80% of the advantage of doing the entire job can be generated. Or in terms of quality improvement, a large majority of problems (80%) are produced by a few key causes (20%).

Pareto analysis is a formal technique useful where many possible courses of action are competing for attention. In essence, the problem-solver estimates the benefit delivered by each action, then selects a number of the most effective actions that deliver a total benefit reasonably close to the maximal possible one.

Pareto analysis is a creative way of looking at causes of problems because it helps stimulate thinking and organize thoughts. However, it can be limited by its exclusion of possibly important problems which may be small initially, but which grow with time. It should be combined with other analytical tools such as failure mode and effects analysis and fault tree analysis for example.

This technique helps to identify the top 20% of causes that need to be addressed to resolve the 80% of the problems. Once the top 20% of the causes are identified, then tools like the Ishikawa diagram or Fish-bone Analysis can be used to identify the root causes of the problems.

The application of the Pareto analysis in risk management allows management to focus on the 20% of the risks that have the most impact on the project.

Steps to identify the important causes using Pareto analysis

·         Step 1: Form an explicit table listing the causes and their frequency as a percentage.

·         Step 2: Arrange the rows in the decreasing order of importance of the causes (i.e., the most important cause first)

·         Step 3: Add a cumulative percentage column to the table

·         Step 4: Plot with causes on x- and cumulative percentage on y-axis

·         Step 5: Join the above points to form a curve

·         Step 6: Plot (on the same graph) a bar graph with causes on x- and percent frequency on y-axis

·         Step 7: Draw line at 80% on y-axis parallel to x-axis. Then drop the line at the point of intersection with the curve on x-axis. This point on the x-axis separates the important causes (on the left) and trivial causes (on the right)

·         Step 8: Explicitly Review the chart to ensure that at least 80% of the causes are captured

Based on the above classification, causes are classified into three categories -

"A"  Class - they are few, therefore, must be controlled tighly. Frequent monitoring is required.

"B" Class - Important causes, significant portion. They can be control by the system.

"C" Class - Many causes but very less efffect. don't take risks, be lazy. Automatic system will take care.

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