Practical guide and verification
Start with counts that share one meaning
A Pareto chart is most useful when every category is measured with the same unit, such as defect count, complaint count, downtime minutes, or cost. Mixing counts and percentages or combining severity scores with event counts can make the descending bars look precise while answering no single question.
Read the cumulative line as prioritization evidence
The cumulative percentage line shows how quickly the largest categories account for the total. The chosen threshold is a planning cutoff, not a law that exactly 20 percent of causes must create 80 percent of effects. Move the threshold when the decision context requires a different coverage target.
Check ties and category definitions before acting
Two bars with equal values can swap order without changing the analysis. More importantly, overlapping or inconsistently defined categories can double-count the same event. Review the source labels before treating the leftmost bars as independent root causes.
Verify the ranked table against the source total
Add the source values independently, then confirm each category share equals value divided by total and that the final cumulative percentage reaches 100 percent apart from rounding. This catches pasted-data omissions and accidental negative or nonnumeric values before export.
Use Pareto analysis to focus investigation, not prove causation
A large bar identifies where measured impact is concentrated; it does not establish why that category is large. Follow the vital-few result with root-cause analysis, process observation, or another suitable investigation before deciding on corrective action.