The Ishikawa Tools – sometimes called the seven basic tools of Six Sigma – are simple but effective tools to address complex quality control challenges. They offer a great place to start for those new to Six Sigma methodology.
Those with a basic understanding of statistics can use the Ishikawa tools. They are named after Japanese engineer Kaoru Ishikawa, an important figure in the development of kaizen (continuing process improvement). The tools are frequently used in quality circles, a term for groups of workers who do similar jobs or work together on an operational process. They meet regularly to identify, analyze and find solutions to work-related problems.
The Ishikawa Tools (Seven Basic Tools)
The following tools make up the Ishikawa Tools. Some may also refer to them as the seven basic tools of Six Sigma.
Cause and Effect Diagram
The cause and effect diagram (also known as a fishbone diagram) provides an easy-to-understand visual that starts with a problem, then lists the causes, sub causes and sub causes of the sub causes until reaching the root cause of the issue. Teams use the fishbone diagram to better solve reoccurring problems.
Check Sheet
A check sheet offers a structured table that allows teams to list problems on the left-hand side, and then provide information on the right of each on the topics such as the frequency and severity of the problem.
Control Chart
A control chart tracks process change over time. Teams use current process data and determine if process variation is consistent (under control) or unpredictable (out of control). If out of control, then teams must use other tools to determine the root cause of the problem.
Histogram
The histogram is a graph that shows frequency distributions for a specific data set. For example, traffic engineers might use a histogram to record the number of people who pass through an intersection at different times of day. A retail outlet might determine staffing levels for every hour of the way by creating a histogram that tracks the number of customers who come through the door at different times on every day of the week.
Pareto Chart
Named after Italian economist Vilfredo Pareto, the Pareto Chart works on the theory that 80% of process problems occur because of mistakes in 20 percent of the factors involved in the process. The Pareto Chart helps teams identify the most significant factors in a process, allowing them to focus on improving the most important aspects of a process.
Scatter Diagram
A scatter diagram involves 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 hurricanes in one year (one data set) and the months of the year they occurred (a second data set). This quickly establishes what months of the year that require the most hurricane preparation.
Stratification
The process of stratification involves taking a data set and breaking it down into categories that provide more insight. For instance, a manager might have data showing the dates that their employees show up late for work. But by further breaking that data down into days of the week, they can quickly see what days where lateness most frequently occurs (Monday, most likely).
