Ishikawa diagram - explanation and definition of Ishikawa diagram.

What is cause and effect diagram - Ishikawa diagram.

The cause – effect diagram is also known as the "diagram of fish bones" due the shape that has it, also is known of Ishikawa by the name of its creator, this diagram was developed to facilitate the analysis of problems by plotting the relationship between an effect and all its causes or factors that cause this effect, for this reason is called "cause – effect diagram" or causal diagram.

This diagram was developed by K. Ishikawa in 1968 and its shape resembles a fish bone (hence its other name), in order to Ishikawa was easy to get a graphic interpretation were to indicate the relationship between one effect and the causes that has produced, so that visually exposed all causes that contributed an effect to the level desired, although in most cases the intention is to get to the root causes.

So Ishikawa diagram is a graph, orderly and systematic way to represent the complex network of possible causes behind one effect. It used to reveal the possible causes associated with an effect, thus facilitating the task of identifying the real factors.

Its applications are varied, as we can read below.

• Identify the root causes, and not just the symptoms, of a given situation and group them into categories.

• Summarizing all the relationships between the causes and effects of a process.

• Promote process improvement.

• Consolidate those ideas of team members on specific activities related to quality.

• Also favor the thought of the team, which will lead to a higher contribution of ideas.

• Get a global and structured vision of a situation as it has been made an identification of a set of basic factors.

Ishikawa diagram develop

In order to properly develop a cause - effect diagram, below expose the steps to follow:

• Define clearly the effect whose causes will be identified and put it in writing

• Draw a long horizontal arrow and place on top the effect defined above.

• Identify the primary factors through brainstorming. Place them around the horizontal arrow and unite to them by slanted lines.

• Write the secondary, tertiary… factors, also through brainstorming method.

• To help determine possible causes can answer the following questions Who? What? Where? When? How? How Much?

• Analyze and select the real causes.

• Test the validity of the causal sequence, ie, starting from the root cause to follow the reasoning investigated effect and ensure that it makes logical sense.

If at the end of develop a diagram it discovered that a branch has few causes compared with others, it may mean that this branch requires further study in depth, due perhaps the team does not know well enough some of the research problem. It is recommended to carefully study this branch if the root cause it was found.

One of the most common mistakes when using cause-effect diagram is taken as real causes that appear without contrasting them with information on the problem under study. The cause-effect diagram is a useful tool for the analysis of causes, but does not replace checking them with real data. Finally is recommended not to begin construction of this diagram until you have analyzed real data of the problem.