Pareto Chart
DE: Pareto-Diagramm
A histogram ordered by frequency based on the 80/20 rule.
Detailed Explanation
A Pareto chart is a special type of histogram ordered by frequency of occurrence that shows how many defects were generated by type or category. It is based on the Pareto principle (80/20 rule) which states that roughly 80% of effects come from 20% of causes.
The chart displays bars in descending order of frequency with a cumulative percentage line. This visual makes it immediately clear which few categories are responsible for the majority of problems. By addressing these top causes, the team achieves the greatest quality improvement with the least effort.
Pareto charts are a core quality management tool used during quality control to prioritize improvement efforts. They complement Ishikawa diagrams — use Ishikawa to identify all potential causes, then Pareto to prioritize which causes to address first based on their frequency or impact.
Key Points
- Based on the 80/20 rule (Pareto principle)
- Bars ordered by descending frequency with cumulative line
- Identifies the vital few causes from the trivial many
- Prioritizes improvement efforts for maximum impact
- Core quality management and control tool
- Complements Ishikawa diagram for root cause analysis
Practical Example
A QC team analyzes 200 production defects. The Pareto chart reveals: 'Configuration errors' (80 defects, 40%), 'Missing validation' (50, 25%), 'UI bugs' (30, 15%), 'Performance issues' (20, 10%), 'Other' (20, 10%). The top 2 categories account for 65% of all defects. The team focuses improvement efforts on configuration management and input validation — addressing these two areas will eliminate nearly two-thirds of all defects.
Tips for Learning and Applying
Address the tallest bars first — they represent the biggest improvement opportunity
Redraw the Pareto chart after improvements to verify the impact
Use Pareto analysis for both defect types and defect causes
Combine with Ishikawa: Pareto tells you WHERE to focus, Ishikawa tells you WHY
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