Active Learning Exercises For Understanding Statistical Process Control

Statistical Process Control (SPC) is a statistical based methodology for distinguishing a real shift in a manufacturing process (assignable cause variation) from random fluctuations (common cause variation). Historical data are used to generate upper and lower control limits. Production samples are selected and measured and the results plotted on a control chart. If the process is unchanged, new sample data should fall between the control limits. If a process shift occurs it becomes more likely that a new data point will be outside of the control limits. The process is improved by eliminating assignable causes and reducing the common cause variation.