ABSTRACT
This chapter introduces the methodology of control charts, specifically the variables charts for average, range, individuals, and standard deviations, and the attribute charts for percentage defective and defects per unit. Control charts are graphical tools that show variation within a process and allowable or expected variation of a process over a period of time. Control charts require that sample values of a particular variable be recorded periodically. Control charts show the control limits for any process. A high reject rate, introduction of a new manufacturing process, customer complaints, or just normal operating procedures may indicate that control charts should be maintained for a particular process. Control charts tell when a process is out of control or not producing as it has in the past. Comparison of control chart data with specifications will reveal whether or not the process is producing acceptable material. When a process is out of control, special causes of variation have entered the process.
