Seven basic tools of quality
The seven basic tools of quality is a designation given to a fixed set of graphical techniques identified as being most helpful in troubleshooting issues related to quality. They are called basic because they are suitable for people with little formal training in statistics and because they can be used to solve the vast majority of quality-related issues.
- Cause-and-effect diagram (also known as the "fishbone diagram" or Ishikawa diagram)
- Check sheet
- Control chart
- Pareto chart
- Scatter diagram
- Stratification (alternatively, flow chart or run chart)
The designation arose in postwar Japan, inspired by the seven famous weapons of Benkei. It was possibly introduced by Kaoru Ishikawa who in turn was influenced by a series of lectures W. Edwards Deming had given to Japanese engineers and scientists in 1950. At that time, companies that had set about training their workforces in statistical quality control found that the complexity of the subject intimidated most of their workers and scaled back training to focus primarily on simpler methods which suffice for most quality-related issues. The Project Management Institute references the seven basic tools in A Guide to the Project Management Body of Knowledge as an example of a set of general tools useful for planning or controlling project quality.
The seven basic tools stand in contrast to more advanced statistical methods such as survey sampling, acceptance sampling, statistical hypothesis testing, design of experiments, multivariate analysis, and various methods developed in the field of operations research.
- Montgomery 2005, p. 148.
- Ishikawa 1985, p. 198: "From my past experience as much as ninety percent of all problems within a company can be solved by means of these tools."
- Tague 2005, p. 15.
- Ishikawa 1985, p. 198: "Elementary Statistical Method (the so-called Seven Tools) 1. Pareto chart: The principle of vital few; trivial many 2. Cause and effect diagram (This is not precisely a statistical technique) 3. Stratification 4. Check sheet 5. Histogram. 6. Scatter diagram (analysis of correlation through determination of median; in some instances, use of binomial probability paper) 7. Graph and control chart (Shewhart control chart)".
- Imai 1986, pp. 239–240: "The seven statistical tools used for such analytical problem-solving are: 1. Pareto diagrams ... 2. Cause-and-effect diagrams ... 3. Histograms ... 4. Control charts ... 5. Scatter diagrams ... 6. Graphs ... 7. Checksheets."
- Ishikawa 1990, p. 98: "They were named the Seven QC Tools after the famous seven weapons of the Japanese Kamakura-era warrior-priest Benkei which enabled Benkei to triumph in battle; so too, the Seven QC Tools, if used skillfully, will enable 95% of workplace problems to be solved. In other words, intermediate and advanced statistical tools are needed in about only 5% of cases."
- Moore, Matthew (30 November 2007). "The Seven Basic Tools of Quality". Improvementandinnovation.com. London. Archived from the original on 19 October 2012. Retrieved 18 May 2013.
- Ishikawa 1985, p. 18: "It is true that statistical methods are effective, but we overemphasized their importance. As a result, people either feared or disliked quality control as something very difficult. We overeducated people by giving them sophisticated methods where, at that stage, simple methods would have sufficed."
- Project Management Institute 2013, pp. 236–238.
- Ishikawa 1985, pp. 198–199: "I divide statistical methods into the following three categories according to their level of difficulty. 1. Elementary Statistical Method (the so-called Seven Tools) ... 2. Intermediate Statistical Method ... 3. Advanced Statistical Method (using computers concurrently)".
- Imai, Masaaki (1986). Kaizen (Ky'zen): The Key to Japan's Competitive Success (1st ed.). New York: Random House. ISBN 978-0-394-55186-9.
- Ishikawa, Kaoru (1985). What Is Total Quality Control? The Japanese Way. Translated by Lu, David J. (1st ed.). Englewood Cliffs, New Jersey: Prentice-Hall. ISBN 978-0-13-952433-2.
- ——— (1990). Introduction to Quality Control (1st ed.). Tokyo: 3A Corp. ISBN 978-4-906224-61-6.
- Montgomery, Douglas (2005). Introduction to Statistical Quality Control. Hoboken, New Jersey: John Wiley & Sons. ISBN 978-0-471-65631-9.
- Project Management Institute (2013). A Guide to the Project Management Body of Knowledge (5th ed.). Newtown Square, Pennsylvania: Project Management Institute. ISBN 978-1-935589-67-9.
- Tague, Nancy R. (2005). The Quality Toolbox (2nd ed.). Milwaukee, Wisconsin: ASQ Quality Press. ISBN 978-1-62198-045-2.