Invented by engineering professor Kaoru Ishikawa, the seven basic tools of Six Sigma – sometimes referred to as the Ishikawa Tools – are simple but effective tools for solving quality control issues. They also provide a great place to start for those new to Six Sigma methodology.
Ishikawa designed the tools for use by those with basic training in statistics. They provide a straightforward way to address complex quality-related issues. For those earning a certificate in Six Sigma or who want to apply Six Sigma tools and techniques to their business challenges, the seven basic tools provide the perfect place to start.
History of the Seven Basic Tools
Experts consider Ishikawa one of the most important figures in the history of continuous process improvement and Six Sigma. He played a key role in transforming the Japanese manufacturing industry and creating a quality control approach that not only focuses on improvement from top to bottom in an organization, but also from the beginning to the end of the product life cycle.
In post-World War II Japan, industry went through a quality control revolution that provided the genesis of what companies still practice today. Ishikawa, who graduated from college with an engineering degree in applied chemistry, became an expert in organizational theory. He is perhaps best known for this creation of the cause and effect diagram, also known as the fishbone diagram.
Another early invention for Ishikawa are quality circles. These involve workers who do similar jobs and meet regularly to discuss work-related challenges and produce solutions. The fishbone diagram became an important tool for quality circles and also one of the seven basic tools.
The seven basic tools first emphasized by Ishikawa all focus on helping teams identify, analyze and solve work-related problems.
The Ishikawa Tools
The Ishikawa Tools, or seven basic tools, are as follows. Each remains an important tool for teams who want a systematic approach to making processes more efficient and effective. They also put the focus on quality, reducing errors, and meeting the needs of customers.
Cause and Effect Diagram
The cause and effect diagram (fishbone diagram) allows teams to list the causes, sub causes and sub cases of sub causes that lead to errors or waste in a process (the Five Whys are often used with a cause and effect diagram).
Check Sheet
A check sheet provides a method to collect and itemize process-related issues for future consideration. It’s essentially a list of all the potential problems causing operational errors. It’s typically in the form of a table with a list of issues on the left-hand column and boxes to the right that can be checked to document when and how often the problem occurs.
Control Chart
A control chart tracks how a process changes over time. By comparing current process data with past data, teams can determine if process variation is consistent (which signifies it is under control) or unpredictable (which signifies it is out of control). The latter means teams must identify the special causes leading to the process variation.
Histogram
The histogram is a frequently used graph that shows frequency distributions for a specific data set. For example, a restaurant or retail outlet might want a histogram of the number of people who enter the establishment at different times of the day in order to determine proper staffing levels.
Pareto Chart
Named after Italian economist Vilfredo Pareto, the Pareto Chart works on the 80-20 theory (80 percent of problems occur because of failure or mistakes in 20 percent of the factors involved in the process). But which factors belong in the 20 percent? The Pareto Chart helps teams identify the most significant factors in a process that require the most attention.
Scatter Diagram
A scatter diagram uses what is known as scatter plots. These involve placing plot points on an X and Y axis for two different sets of data, providing a visual that quickly can show the relation between two sets of data. A simple example is a chart of the hurricanes within a given year (one data set) and the months of the year when they occur (a second data set). It’s easy to quickly see a relationship between the summer months and hurricanes.
Stratification
The process of stratification involves taking a data set and breaking it down into categories that provide more insight. For example, a pizza delivery business might have data showing that they were late on deliveries most frequently on certain dates of the month. However, by breaking down the data into categories of days of the week, they may find that the bulk of the late deliveries happened on Saturday afternoon when they had only one driver working. They learn Saturday afternoons are busier than they thought, and add a second driver to avoid frequent late deliveries.
Once people learn how to apply them correctly, these seven basic tools provide simple-but-powerful ways to analyze and make use of data. As Ishikawa intended, they give people more control over a process, allowing them to continually make improvements.
