Last quarter we sat in on a weekly quality meeting at a medical device subcontractor in Osan. The team spent forty minutes debating a Pareto chart showing solder bridge defects at 18% of total rejects. A run chart of the same data would have shown the rate climbing for six consecutive weeks — a pattern the Pareto alone obscured.
Use Pareto when prioritizing corrective actions
Pareto charts rank categories by cumulative impact. They answer: where should we spend our limited engineering hours this month? They do not answer whether a category is getting better or worse over time.
Use run charts when tracking a single metric over weeks
Plot weekly first-pass yield, customer ppm, or scrap cost index on a run chart with a median line. Look for shifts and trends before diving into category breakdowns.
Using both in sequence
We advise clients to open with one run chart of the headline KPI, then drop to a Pareto only if the run chart shows deterioration. This sequence cut one client's meeting from 75 to 35 minutes without losing audit traceability.