A Pareto chart is a tool which is used to analyze the relative frequency of deviations from specifications or success criteria. The Pareto chart is a frequency histogramA bar graph that shows frequency of occurrence versus value. Quite often the data is fitted to a distribution such as a normal distribution. . which is ordered from highest to lowest. Unlike control and capability charts, this chart uses no statistical guides.
Pareto charts emphasize Pareto's empirical law that any assortment of events consists of a few major and many minor elements. In the context of SQC, it is important to select the few vital major opportunities for improvement from the many trivial minor ones. The Pareto chart is particularly useful for Cost-to-fix versus Deviation-frequency analysis.
In addition to the histogram, typically a cumulative percentage is also given. From top to bottom, the percentage represents the ratio of the sum of evry value to this point, to the sum of every value in the chart.