4.3.3 Chart of the reasons and results

The result of process depends on numerous factors between which there are relations like reason - result. It is possible to define structure or character of these multiple-factor relations thanks to systematic supervision. It is difficult to solve complex problems, without knowing this structure which represents the purpose of the reasons and results. The chart of the reasons and results - the means allowing to express these relations in a simple and available form.

In 1953 professor of the Tokyo university to Cahors Isikava, Discussing a quality problem at one plant, summarized opinion of engineers in the form of the chart of the reasons and results. It is considered that then this approach was applied in the first, but even earlier employees professors of Isikava used this method for streamlining of factors in the scientifically - research work. When the chart started being used in practice, it was very useful and was widely adopted in many companies of Japan soon. It was included in the Japanese industrial standard (JIS) on terminology in the field of quality control and is defined in it as follows: the chart of the reasons and results - the chart which shows the attitude between an indicator of quality and the factors influencing it.

Now this chart is used around the world not only in relation to indicators of quality of production, but also in other areas.

How to construct the chart of the reasons and results?

To construct the chart of the reasons and results - difficult business. Rightfully it is possible to declare that those who succeeded in the solution of problems of quality control, is just those who mastered creation of the present charts. There are many ways of their construction, but two most typical will be considered here. Before starting the description of procedure of their construction on an example, we will explain their structure.

Structure of the chart of the reasons and results and concrete example

The chart of the reasons and results differently call "a fish skeleton" as it reminds a skeleton of fish that is visible in figure 3.2. Sometimes it is also called "tree" or the chart of "river inflows". Let's use the name "fish skeleton". The concrete example is given on figure 2.3.

Figure 2.4 Structure of the Chart of the Reasons and result

Figure 2.5 Example of the Chart of the Reasons and Results

Method of creation of charts of the reasons and results for definition of the reasons

1. Procedure

Stage 1

Define a quality indicator

Stage 2

Choose one indicator of quality and write it in the middle of the right edge of a clean sheet of paper. From left to right draw a straight line ("ridge"), and conclude the written-down indicator in a rectangle. Further write the main reasons which influence a quality indicator, conclude them in a rectangle and connect to "spine" shooters (in a look) "big bones of ridge".

Stage 3

Write the reasons (secondary) influencing the main reasons ("big bones"), and arrange them in the form of the "average bones" adjoining to "big". Write the reasons of a tertiary order which influence the secondary reasons, and arrange them in the form of the "small bones" adjoining "averages".

Stage 4

Range factors on their importance and allocate especially important which allegedly have the greatest impact on a quality indicator.

Stage 5

Write down all necessary information.

2. Procedure explanations

Putting this procedure into practice, it is possible will meet difficulties. The best way in this case - to consider a problem from the point of view of "variability". For example, when you think of "big bones", argue about changes in a quality indicator. If data show that changes exist, think why so occurs. Change of result can be caused by changes in factors. Such turn in thoughts is very effective.

When build the chart of the reasons and results in relation to concrete defect, for example, it is possible to find out that number of the defects allowed different days of week, variously. If it is found out that defects meet on Monday, than in other days of week more often, it is possible to ask a question: "And why defects on Monday are allowed more often than in other days of week", "Why they arise?". It will force to pay attention to consideration of factors which distinguish Monday of other days of week that as a result will lead to detection of the reason of defect.

Having resorted to such way of a reasoning at each stage of research of the relations between an indicator of quality and "big bones", between "big" and "average", and also between the last and "small bones", perhaps logical way to construct the useful chart of the reasons and results.

After creation of the chart, the following step - distribution of factors on degree of their importance. Not necessarily all factors included in the chart will have strong impact on a quality indicator. Designate what make the greatest impact.

And at last, on the chart all necessary information: its name, name of a product, process or group of processes, names of participants of process, date, etc.

Procedure of creation of the chart of the reasons and results for systematization of the list of the reasons

1. Procedure

Stage 1

Solve, what indicator of quality will be investigated.

Stage 2

Find as much as possible number of the reasons which, perhaps, influence this indicator.

Stage 3

Consider the relations between the reasons and construct the chart, jointing its elements on the basis of the relations the reason - result with a quality indicator.

Stage 4

Establish importance of each factor and note major factors which, make the greatest impact on a quality indicator.

Stage 5

Write down all necessary information.

2. Procedure explanation

Such approach is characterized by a combination of two different types of activity: search of the greatest possible number of the reasons and their systematization.

For search of the reasons carry out, in case of need, active discussion. The "brain storm" which is thought up in the USA by A.F. Osborn will be the effective method applied in that case.

At creation of the chart of the reasons and results it is better to systematize, considering their sequences: from "small bones" to "averages" and from "averages" to "big".