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SAS/QC Software

Basic Problem Solving

Basic problem-solving methods play a key role in modern statistical quality improvement applications. Since the 1960s, workers and engineers in Japanese industry have used simple graphical displays, referred to as the "basic seven QC tools" or the "magnificent seven QC tools," to analyze data and present the results of their problem-solving activities. These displays are now universally taught as tools for organization-wide quality improvement activities, and they are often incorporated in large-scale systems for statistical process control.

The "basic seven QC tools" are check sheets, Pareto charts, Ishikawa diagrams, flow diagrams, histograms, scatter plots, and control charts.

Pareto Charts

Before-and-After Pareto Chart
Before-and-After Analysis Using a Comparative Pareto Chart


The Pareto chart, used to determine priorities for quality improvement activities, is a bar chart that displays the relative frequency of problems in a process or operation. Each bar represents the relative frequency of a problem, and the bars are arranged in decreasing order from left to right. Sometimes a curve is superimposed to indicate the cumulative percent of problem frequencies. The chart is named after Vilfredo Pareto (1848-1923), an Italian economist.

Pareto charts provide a tool for visualizing the Pareto principle, which states that a small subset of problems (the "vital few") that affect a common outcome tend to occur much more frequently than the remainder (the "useful many"). A Pareto chart can be used to decide which subset of problems should be solved first, or which problems deserve the most attention. Pareto charts are often constructed to provide a before-and-after comparison of the effect of control or quality improvement measures.

You can also produce Pareto charts in the SQC Menu System.

Ishikawa Diagrams

Ishikawa Diagram
Ishikawa Diagram


The Ishikawa diagram, also referred to as a cause-and-effect diagram, tree diagram, or fishbone diagram, displays the factors that affect a particular quality characteristic, outcome, or problem. The diagram is named after its developer, Kaoru Ishikawa (1915-1989), a leader in Japanese quality control.

An Ishikawa diagram is typically the result of a brainstorming session in which members of a group offer ideas about how to improve a product, process, or service. The main goal is represented by the trunk of the diagram, and primary factors are represented as branches. Secondary factors are then added as stems, and so on. Creating the diagram stimulates discussion and often leads to increased understanding of a complex problem. Japanese QC Circle members often post Ishikawa diagrams in a display area where they are accessible to managers and other groups. In the United States, Ishikawa diagrams are included in presentations by plant personnel to management or customers.

You can also produce Ishikawa diagrams in the SQC Menu System.