Results 211 to 220 of about 5,815 (232)

A Multivariate Sign EWMA Control Chart

Technometrics, 2011
Nonparametric control charts are useful in statistical process control (SPC) when there is a lack of or limited knowledge about the underlying process distribution, especially when the process measurement is multivariate. This article develops a new multivariate SPC methodology for monitoring location parameters.
Zou, Changliang, Tsung, Fu-gee
openaire   +2 more sources

The Improved EWMA Chart for Heteroscedasticity Process

Annals of Data Science, 2017
It is doubtful of the validity of the EWMA chart that the observations from heteroscedasticity processes violate the assumption of identical distribution. In this paper, we discuss the effect of heteroscedasticity on the performance of the conventional EWMA chart.
Dan Zhou, Liu Liu, Xin Lai
openaire   +1 more source

Some issues in the design of EWMA Charts

Communications in Statistics - Simulation and Computation, 2000
The traditional design procedure for selecting the parameters of EWMA charts is based on the average run length (ARL). It is shown that for some types of EWMA charts, such a procedure may lead to high probability of a false out-of-control signal.
Lai K. Chan, Jian Zhang
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An EWMA chart for monitoring process mean

Journal of Statistical Computation and Simulation, 2018
ABSTRACTIn the statistical process control literature, there exists several improved quality control charts based on cost-effective sampling schemes, including the ranked set sampling (RSS) and median RSS (MRSS). A generalized cost-effective RSS scheme has been recently introduced for efficiently estimating the population mean, namely varied L RSS ...
Muhammad Awais, Abdul Haq
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Designing a Multivariate EWMA Control Chart

Journal of Quality Technology, 1997
A multivariate exponentially weighted moving average control chart can be used to improve the detection of small shifts in multivariate statistical process control. Recommendations are provided for the selection of parameters for such a chart. The recom..
Sharad S. Prabhu, George C. Runger
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An EWMA mean chart with auxiliary information

Quality and Reliability Engineering International, 2023
AbstractIn this paper, we show that a recently proposed auxiliary information‐based (AIB) adaptive EWMA (AE) chart is sensitive (not robust) to the changes in the mean of an auxiliary variable when monitoring the changes in the mean of a quality variable, called the AIB‐AE chart.
openaire   +1 more source

An insight into control charts using EWMA

Communications in Statistics - Theory and Methods, 2021
In this discussion, an insight into MA-EWMA based control chart is given. The two approaches for MA-EWMA control chart are discussed and compared with each.
openaire   +1 more source

Multivariate EWMA Charts with Variable Sampling Intervals

Economic Quality Control, 2009
Summary: The standard multivariate control chart usually employs fixed sample sizes at fixed sampling intervals (FSI) to monitor a process. In this study, a multivariate exponentially weighted moving average (MEWMA) chart with variable sampling intervals (VSI) is investigated.
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EWMA control charts for autoregressive processes

Journal of the Operational Research Society, 2001
Summary: Many processes must be monitored by using observations that are correlated. An approach called algorithmic statistical process control can be employed in such situations. This involves fitting an autoregressive-moving average time series model to the data. Forecasts obtained from the model are used for active control, while the forecast errors
Koehler, A. B., Marks, N. B., O'Connell, R. T.   +2 more
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EWMA Charts Reliability in Multicavity Processes

Quality Engineering, 2005
ABSTRACT Using Shewart charts to control multicavity processes is not, in general, reliable when there are small deviations in relation to the total variability and when there is a large number of cavities. For this reason EWMA charts have been used to control averages and standard deviations in some of the cavities.
Miquel Salicrú, Juan J. Barreiro
openaire   +1 more source