Control charts with exponentially weighted moving average (EWMA) statistics (mean and variance) are used to jointly monitor the mean and variance of a process. An EWMA cost minimization model is presented to design the joint control scheme based on pure economic or both economic and statistical performance criteria. The pure economic model is extended to the economic-statistical design by addin...

Statistical process control (SPC) requires statistical methodologies that detect changes in the pattern of data over time. The common methodologies, such as Shewhart, cumulative sum (cusum), and exponentially weighted moving average (EWMA) charting, require the in-control values of the process parameters, but these are rarely known accurately. Using estimated parameters, the run length behavior...

Article history: Received 28 March 2010 Received in revised form 14 February 2012 Accepted 16 April 2012 Available online 25 April 2012

Control charts are powerful tools to monitor quality characteristics of services or production processes. However, in some processes, the performance of process or product cannot be controlled by monitoring a characteristic; instead, they require to be controlled by a function that usually refers as a profile. This study suggests employing exponentially weighted moving average (EWMA) and range ...

Charts for Autocorrelated Processes Hyun Cheol Lee Samsung Electronics, Semiconductor Business Quality Assurance Dept. Banwol-Dong, Hwasung-City Gyeonggi-Do, Korea 445-701 Phone: 82-31-208-4717 Fax: 82-31-208-6699 Email: [email protected] Daniel W. Apley (Corresponding Author) Department of Industrial Engineering and Management Sciences Northwestern University Evanston, IL 60208-3119 Phone: 8...

Diagnostic laboratories are increasingly required to meet stringent quality standards, and validated assays are needed to achieve formal accreditation. Validation of test methods is often considered to be finalised when the assay parameters and characteristics have been established. However, like any process, diagnostic assays are subject to random variation resulting in shifts in the mean test...

Residual-based control charts are popular methods for statistical process control of autocorrelated processes. To implement these methods, a time series model of the process is required. The model must be estimated from data, in practice, and model estimation errors can cause the actual in-control average run length to differ substantially from the desired value. This article develops a method ...