A
Pareto chart is a special type of bar chart where
the values being plotted are arranged in descending order. The graph is accompanied by a line graph which shows the cumulative totals of each category, left to right. The chart is named after
Vilfredo Pareto, and its use in
quality assurance was popularized by
Joseph M. Juran and
Kaoru Ishikawa.
The Pareto chart is one of the seven basic tools of quality control, which include the
histogram, Pareto chart,
check sheet,
control chart,
cause-and-effect diagram,
flowchart, and
scatter diagram. See
glossary of quality management. These charts can't be generated in MS office or Open office tools without difficulties. It is possible to use one of the software tools or one of free "online quality chart generators" instead.
Typically on the left vertical axis is frequency of occurrence, but it can alternatively represent cost or other important unit of measure. The right vertical axis is the cumulative percentage of the total number of occurrences, total cost, or total of the particular unit of measure. The purpose is to highlight the most important among a (typically large) set of factors. In
quality control, the Pareto chart often represents the most common sources of defects, the highest occurring type of defect, or the most frequent reasons for customer complaints, etc.
Their use gives rise to the
80-20 Rule — that 80 percent of the problems stem from 20 percent of the causes.
Simple example of a
Pareto chart using hypothetical data showing the relative frequency of reasons for arriving late at work.
