Seven Basic Tools of Quality

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."

Cause-and-effect diagram
Identifies many possible causes for an effect or problem and sorts ideas into useful categories [also called Ishikawa or fishbone chart]
Check sheet
A structured, prepared form for collecting and analyzing data; a generic tool that can be adapted for a wide variety of purposes
Control charts
Graphs used to study how a process changes over time
Histogram
The most commonly used graph for showing frequency distributions, or how often each different value in a set of data occurs
Pareto chart
Shows on a bar graph which factors are more significant
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")

Excerpted from Nancy R. Tague's The Quality Toolbox, Second Edition, ASQ Quality Press, 2004, page 15.