Introduction
The PARETO procedure creates Pareto charts,
which display the relative frequency of quality-related
problems in a process or operation. The frequencies
are represented by bars that are ordered in decreasing
magnitude. Thus, a Pareto chart can be used
to decide which subset of problems should be solved first
or which problem areas deserve the most attention.
Pareto charts provide a tool for visualizing the Pareto
principle,*
which states that a small subset of problems tend to
occur much more frequently than the remaining problems.
In Japanese industry, the Pareto chart is one of the
"seven basic QC tools" heavily used by workers
and engineers. Ishikawa (1976) discusses how to
construct and interpret a Pareto diagram. Examples of
Pareto diagrams are also given by Kume (1985) and
Wadsworth and others (1986).
You can use the PARETO procedure to
- construct Pareto charts from unsorted raw data
(for instance, a set of quality
problems that have not been classified into
categories) or from a set of distinct
categories and corresponding frequencies
- construct Pareto charts based on the percentage of
occurrence of each problem, the frequency (number
of occurrences), or a weighted frequency (such as
frequency weighted by the cost of each problem)
- add a curve indicating the cumulative
percentage across categories
- construct side-by-side Pareto charts or stacked
Pareto charts
- construct comparative Pareto charts
that enable you to compare the Pareto
frequencies across levels of one or two
classification variables. For example, you can
compare the frequencies of problems encountered
with three different machines for five consecutive
days.
- highlight the "vital few" and the
"useful many"* categories by using different colors
for bars corresponding to the n most
frequently occurring categories or the m least frequently
occurring categories.
- create charts with bars oriented vertically or horizontally
- highlight special categories by using different colors
for specific bars
- create charts using either a high-resolution graphics
device or a line printer
- annotate charts created on graphics devices
- inset summary statistics in charts created on graphics devices
- save charts created on graphics devices in a graphics
catalog for subsequent replay
- display sample sizes on Pareto charts
- display frequencies above the bars
- define characters used for features on plots produced
on line printers
- save information associated with the categories
(such as the frequencies) in an output data set
- restrict the number of categories displayed
to the n most frequently
occurring categories
