Basic quality 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 analyse data and present the results of their quality 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.
The Pareto chart is used to determine priorities for quality improvement activities. It 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”) affecting a common outcome tends to occur much more frequently than the remainder (the “useful many”). The 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.