Statistical process control (SPC) has been used to achieve and maintain control of various processes in industry (Stoumbos, Reynolds, Ryan, and Woodall 2000). The control chart is a primary SPC tool to monitor process variability and promote quality improvement by means of detecting process shifts requiring corrective actions. As a graphical monitor, control charts generally contain a centerlin...

This study evaluated the preparation of Shewhart's control charts using the concept of rational subgroups for monitoring the Salmonella antibody ELISA used for surveillance of Danish pig herds. Control charts were prepared for a buffer control sample, a negative serum sample and a positive serum sample. The quality control variables were the natural logarithm (In) of the uncalibrated optical de...

Attribute control charts (e.g., charts for counts and proportions) have discrete jumps in the quantities plotted on the charts, which means that the chart designer has only a discrete set of unique control limits to choose from when designing a chart. These charts have a small set of in-control Average Run Lengths (ARLs) from which to determine the appropriate control scheme. In a chart with ra...