ASQ — Seven Basic Quality Tools: The Series
No prequel or sequel, ASQ has made available to the members and the public a huge amount of information on the "quality" body of knowledge (BOK). Amongst them, Quality Tools. These are defined as instruments or techniques to support and improve the activities of quality management and improvement. ASQ's quality tools articles can help you find new ways to identify causes, understand processes, collect and analyze data, generate ideas, keep projects on track, and make informed decisions for all of your continuous improvement activities.
In this series of articles, we will present the 7 Basic Quality Tools for Process Improvement used in the field. They were developed and refined over the years, but their simplicity and relatively high impact in sorting data and resolving process issues has kept them in 'business' over the years. The purpose of this small series of articles is to introduce/re-introduce them to you as well as point you to resource links to ASQ's website. It is only meant to be as a starting point, but oh so useful.
Definition: Seven tools of quality ("The Old Seven." "The First Seven." "The Basic Seven.")
Quality pros have many names for these seven basic tools of quality, first emphasized by Kaoru Ishikawa, a professor of engineering at Tokyo University and the father of "quality circles." Start your quality journey by mastering these tools, and you'll have a name for them too: indispensable.
- Check sheet: A structured, prepared form for collecting and analyzing data; a generic tool that can be adapted for a wide variety of purposes.
- Histogram: The most commonly used graph for showing frequency distributions, or how often each different value in a set of data occurs.
- Pareto chart: A bar graph that shows which factors are more significant.
- Control chart: Graph used to study how a process changes over time. Comparing current data to historical control limits leads to conclusions about whether the process variation is consistent (in control) or is unpredictable (out of control, affected by special causes of variation).
- Cause-and-effect diagram (also called Ishikawa or fishbone diagrams): Identifies many possible causes for an effect or problem and sorts ideas into useful categories.
- Scatter diagram: Graphs pairs of numerical data, one variable on each axis, to look for a relationship.
- Stratification: A technique that separates data gathered from a variety of sources so that patterns can be seen (some lists replace stratification with flowchart or run chart).