7 Quality Control Tools
The 7 Quality Control Tools are a set of graphical techniques used to identify and analyze sources of variation within a manufacturing process. The tools are sometimes referred to as “Japanese Seven Tools of Quality Control.” These tools are useful for problem solving and allow for the investigation of root causes of deficiencies in product or process quality. To understand the 7 Quality Control Tools, it is important to understand the concept of quality control in general. Once the nature of quality control has been established, the specific tools used in quality control can be explored.
Quality control is the process of ensuring that product quality meets established standards of quality. This is accomplished through various activities such as inspection, testing, sampling and data analysis. Quality control also involves setting product and process specifications, developing certification procedures, verifying compliance with quality standards and implementing corrective action programs. Quality control programs are typically divided into two categories: functional and statistical. Statistical quality control involves evaluating products statistically by collecting and analyzing data to ensure that products meet predetermined standards. Quality control teams use a combination of both functional and statistical methods.
The 7 Quality Control Tools are a data analysis system developed and promoted in Japan in the late 1950s for analyzing the causes and solutions for problems in a manufacturing process. The seven tools are: check sheets, Pareto diagrams, cause-and-effect diagrams, control charts, histograms, flow diagrams, and scatter diagrams.
The check sheet is a simple form used to help systematically organize and track data. A check sheet is typically used to collect data about process performance over time or as part of a specific inspection. This tool is used to identify patterns of occurrences in a data set, locate sources of error and identify potential solutions.
A Pareto diagram is used to display the most significant sources of error in a graphical format. It is constructed by sorting sources of variation from greatest to least and plotting them on Y-axis of a bar chart. The X-axis represents the percentage of the total observed variation accounted for by the source.
Cause-and-effect diagrams, also known as Ishikawa or fishbone diagrams, are diagrammatic tools used to identify potential causes of process errors. The tool is typically created by drawing a diagram of a fish with the problem being researched as the head of the fish. From the head, lines lead to possible sources of the problem, allowing for focused investigation.
Control charts are a tool used to observe process performance over time. Control charts contain data points which are plotted on a graph. The plotted points allow for variations in process performance to be observed and trends to be identified.
Histograms are graphical representations of data which are collected over a predetermined period of time. This tool is used to understand the shape of data distribution, to detect shifts in process performance and to specify the upper and lower control limits.
Flow diagrams, also known as process maps, are simply diagrams which show the flow of a process. Flow diagrams are used to understand the sequence of activities in a process and to identify potential sources of variation.
The last tool in the set of 7 Quality Control Tools is the scatter diagram. This tool is used to identify relationships between two variables in a process. Scatter diagrams are plotted using X and Y axes to illustrate the correlation between the two variables.
The 7 Quality Control Tools have been used by many organizations for many years to achieve and maintain quality in manufacturing processes. These tools are relatively simple to understand and to put into practice. With the proper training, organizations can begin to see the value in the use of these tools and implement them into their existing quality control systems.
