Statistical Process Control

Toni White

March 28, 2010


Week 5 – Statistical Process Controls

Statistical Process Control

      Total Quality Management is a philosophy that stresses three principles for achieving high levels of process performance and quality: Customer Satisfaction, Employee Involvement, and Continuous Improvement in Performance.   This paper will address a practical type of continuous improvement - the use of statistical process control.
      One definition of statistical process control (SPC) is “the application of statistical techniques to determine whether a process is delivering what the customer wants” (Goetsch & Davis, 2006).   SPC primarily involves using control charts to detect defective services or products or to indicate that the process has changed and that the same services or products will deviate from their design specifications unless corrections are made. For example, in this paper we will examine
      • A decrease in the average number of calories consumed on a daily basis,

Control Charts

      SPC may be broadly broken down into three sets of activities: understanding the process; understanding the causes of variation; and elimination of the sources of special cause variation.   In understanding a process, the process is typically mapped out and monitored using control charts.   Control charts are used to identify variation that may be due to special causes, and to eliminate concern over variation due to common causes.
When, through the control charts, variation that is due to special causes is identified, or the process capability is found lacking, additional effort is exerted to determine causes of that variance and eliminate it. The tools used include Ishikawa diagrams, designed experiments and Pareto charts (Wheeler, 1999).
      Once the causes of variation have been determined, elimination of those causes that are both statistically and practically significant must occur. Typically, the elimination process includes...