List your defects or causes with their counts and see the few that cause most of the problem.
| Category | Count | |
|---|---|---|
| # | Category | Count | % | Cum % | Status |
|---|---|---|---|---|---|
| 1 | Dimensional error | 42 | 42.0 | 42.0 | Vital Few |
| 2 | Surface defect | 28 | 28.0 | 70.0 | Vital Few |
| 3 | Wrong material | 15 | 15.0 | 85.0 | Vital Few |
| 4 | Assembly fault | 9 | 9.0 | 94.0 | Useful Many |
| 5 | Packaging damage | 6 | 6.0 | 100.0 | Useful Many |
A Pareto chart sorts problem categories (defect types, causes, complaint reasons, downtime reasons) from the largest to the smallest and draws the cumulative percentage line over the bars. It shows the “vital few” categories that account for most of the problem, so you fix those first instead of spreading effort over everything. Small categories at the end can be grouped into one “Other” bar.
The 80/20 split is a rule of thumb, not a law. Use the chart to choose where to start, and count by cost or severity instead of frequency when one type of defect matters much more than another.
The chart follows the classic Pareto analysis used in quality management, and is tested with hand-calculated cases, including ties and repeated category names.
The data behind “Try an example”: 100 rejected parts in five defect types.
| Category | Count | Cumulative % |
|---|---|---|
| Dimensional error | 42 | 42 |
| Surface defect | 28 | 70 |
| Wrong material | 15 | 85 |
| Assembly fault | 9 | 94 |
| Packaging damage | 6 | 100 |
The vital few are the first three categories: together they are 85% of the rejects, so that is where the improvement effort should start.