The Shewhart control chart is for many people the embodiment of statistical process control (SPC). In the past, many modifications and improvements have been devised (see Woodall and Montgomery [1999] for a brief overview). Several modifications or additions were aimed at more power for out-of-control situations. Among the earlier additions belong the runs rules from the Western Electric Compan...

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...

The design of control charts in statistical quality control addresses the optimal selection of the design parameters such as the sampling frequency and the control limits; and includes sensitivity analysis with respect to system parameters such as the various process parameters and the economic costs of sampling. The advent of more complicated control chart schemes has necessitated the use of M...

Introduction The outcome of thyroid surgery is usually assessed according to two major complications: recurrent laryngeal nerve paralysis and hypoparathyroidism. The purpose of the study was to monitor the outcomes of thyroid surgery using Shewhart control charts, and then to identify possible ways to improve quality by exploring the special causes of variation in the observed complication rate...

Control charts are themost extensively used technique to detect the presence of special cause variations in processes. They can be classified intomemory andmemoryless control charts. Cumulative sum and exponentially weightedmoving average control charts are memory-type control charts as their control structures are developed in such a way that the past information is not ignored as it is done i...

In the past few years, there has been an increasing interest in developing project control systems. The primary purpose of such systems is to indicate whether the actual performance is consistent with the baseline and to produce a signal in the case of non-compliance. Recently, researchers have shown an increased interest in monitoring project’s performance indicators, by plotting them on the S...

We propose a Shewhart control chart based on gauging theoretically continuous observations into multiple groups. This chart is designed to monitor the process mean and standard deviation for deviations from stability. By assuming an underlying normal distribution, we derive the optimal grouping criteria that maximizes the expected statistical information available in a sample. Control charts ba...

Shewhart control charts have previously been suggested as a process control tool for use in routine linear accelerator (linac) output verifications. However, a comprehensive approach to process control has not been investigated for linac output verifications. The purpose of this work is to investigate a comprehensive process control approach to linac output constancy quality assurance (QA). The...

The most well-known uni-arribute control chart used to monitor the number of nonconformities per unit is the Shewhart type C-chart. In this paper, a new method is proposed in an attempt to reduce the false alarm rate in the C-chart. To do this, the decision on beliefs (DOB) concept is first uti [1] Corresponding author e-mail: [email protected]   lized to design an iterative method, where...