The seven basic quality tools are simple graphical techniques that solve most everyday quality problems. Kaoru Ishikawa popularised them so that every employee, not only specialists, could analyse problems with data.
The tools
- Check sheet: a structured form for counting events where they happen, such as defects by type and shift.
- Pareto chart: a bar chart sorted from largest to smallest that shows the vital few causes.
- Cause-and-effect (fishbone) diagram: organizes possible causes into categories such as method, machine, material, people, measurement and environment.
- Histogram: shows the shape, centre and spread of data.
- Scatter diagram: shows whether two variables move together.
- Control chart: separates normal variation from special causes over time (the Shewhart chart).
- Flowchart or stratification: shows the process steps, or splits data by source to reveal hidden patterns.
A simple sequence
Collect data with a check sheet, prioritize with a Pareto chart, brainstorm causes with a fishbone, test suspected causes with scatter diagrams or histograms, and monitor the fix with a control chart.
