ASQ’s Pareto guidance describes categories ordered by size, often accompanied by cumulative totals. The table below applies the method to fictional shipping incidents; it is not WTM performance data.
Choose one counting rule
Decide whether you count shipments affected or separate events. One shipment might have an address correction and a missed appointment. Counting both events is legitimate for an event-based analysis, but the result should not be labelled the number of delayed shipments.
Use a defined reporting period and mutually understandable categories. An “other” category can help initially, but a large unexplained group deserves further investigation.
A worked example
Assume 40 incidents, each assigned one primary category for this exercise.
The first two categories account for 70%, not 80%. That is the finding. The first three account for 85%. Do not rename categories just to produce a familiar rule.
The calculation for each share is category count divided by 40. Cumulative share adds those percentages in ranked order. Rounding can create a small display difference, so retain underlying counts.
Frequency is not the whole priority decision
A common minor correction may cost less than a rare severe problem. Repeat the analysis with a clearly defined cost or delay measure when that helps the decision. Keep the views separate: a count chart and a cost chart answer different questions.
Do not assign invented costs to make a category look important. Record measured costs, labelled estimates and unknown amounts distinctly. A low-frequency issue may still require immediate action because of its consequences.
Move from a large category to an explanation
“Incomplete release information” identifies where to investigate; it does not explain why the information was incomplete. Look at examples and the underlying workflow. A cause-analysis method such as the 5 Whys can help test a proposed explanation.
Choose one improvement, define the expected effect and review a comparable later period. If shipping volume doubles, compare an appropriate incident rate as well as absolute counts. Fewer incidents during a quiet week may not represent an improved process.
Use shipment records consistently
Keep the shipment reference, incident category, stage, supporting evidence and impact in a simple log. WTM customers can connect relevant shipment documents and delivery history with their internal records, avoiding several names for the same event.
Must the categories follow an 80/20 pattern?
No. The method shows concentration in your data; it does not guarantee a particular split.
Should I always fix the largest category first?
Not automatically. Consider impact, urgency, feasibility and the quality of the evidence alongside its size.
