The Seven Basic Tools of Quality

Many will wonder why seven?

The explanation comes from Japanese history, which tells us the samurai, Japanese warriors, used seven tools or weapons in their military activity.

Inspired by this tradition, Dr Kaoru Ishikawa, an expert in quality control, established seven basic tools (six of statistics and one, the cause-effect diagram, of analysis):

1. The cause-effect diagram, also called the Ishikawa diagram or fishbone, is a simple graphic representation of the mind map model. What are the causes, problems or thorns to analyze, and how do they relate to the problem or effect? With this well-developed analysis tool, we can analyze the relationship between a quality indicator and the factors contributing to its existence
2. Data collection and/or a collection sheet, such as the name indicates, is used to gather data and classify it according to certain categories, by annotating and recording frequencies in the form of data
3. A histogram is a graphic giving a clear view of the system’s variables. It will allow us to display and compare the results of a change in the system, identify abnormalities and, in short, clarify objectives, the quality of a product, the performance of a process or the impact of an improvement action
4. The Pareto chart, or the 80-20 rule, will facilitate decision-making based on the priority of the problems or the causes that generate them. According to Vilfredo Pareto, “80% of problems can be solved, if 20% of the causes are eliminated”
5. Stratification. All information must be stratified according to specific departments and actions to assure the factors assumed and the isolation of the cause of a problem. Each group is a stratum and defined according to the specific situation that needs to be analyzed. Its representation is usually done through a histogram
6. A scatter plot. This graphic tool allows identification of any kind of relationship between two variables. Calculating the correlation coefficient can determine the degree of relationship between the two, and if it is negative, good or null
7. A control chart is used to evaluate the stability of a process and detect random or specific causes of variation

These tools are not intended to replace employee or expert experience, intuition, authority or determination, but to assist in data collection and analysis to make decisions based on them, thus solving most problems in the productive areas.

This does not mean that, with every problem, we use all seven tools at the same time. Two or three may be enough. In fact, there are more but it has been observed that with these seven, it is possible to solve most problems.

For Master Ishikawa, quality had to be a revolution of management, consisting of “developing, designing, elaborating and maintaining a quality product that is the most economical and most useful, which is always satisfactory for the consumer.”

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