Keller, Paul A.; Runger, Dr. George C. (1995, ASQC) Qualaity America, Inc., Tucson, AZ 85710
This abstract is an edited version of the author's original.
Change presents opportunities for improvement. The quality improvement tools used to manage and measure service processes should include process indicators capable of identifying changes in process behavior and identifying causes for the change. It is necessary to differentiate between unstable conditions and the random fluctuation of a stable process.A statistical control chart can determine whether a process is stable or unstable. In the X-bar Chart, the statistic plotted is the average measured level of the process at each point in time, obtained from several observations (called a subgroup). In another popular chart for measured data, the Individual-X Chart, the statistic plotted is a single observation from the process. If observations are not measurements, but rather counts of occurrence, attribute control charts may be appropriate, including the P- chart, Np-chart, C-chart, or U-chart.
The net outcome of a process may not be a good process indicator. In general, a good quality indicator should be easy and economical to measure, provide information useful for process improvement, prevent poor quality, and be sensitive to process change.
Design of experiments (DOE),Management,Statistical process control (SPC),Shewhart control chart,Metrics