Memory-type control charts in statistical process control

Control chart is the most important statistical tool to manage the business processes. It is a graph of measurements on a quality characteristic of the process on the vertical axis plotted against time on the horizontal axis. The graph is completed with control limits that cause variation mark. Once a measurement is outside the control limits, the process is declared out-of-control. Control Charts are widely used in the IC industry, for example in the monitoring of the thickness of silicon slices after a grinding process. Nasir Abbas examines two main control charts using all measurements and shows how they can be improved by additional signaling rules. He also has combined two control structures into a single chart that is gives faster detection ability than the individual structures, when the process is out-of-control. Abbas also developed a new control chart based on the moving average and studied the statistical properties in his thesis.