Results 241 to 250 of about 420,626 (277)

Monitoring the Coefficient of Variation Using EWMA Charts

Journal of Quality Technology, 2011
The coefficient of variation (CV) is a quality characteristic that has several applications in applied statistics and is receiving increasing attention in quality control. This paper suggests a new method to monitor the CV.
CASTAGLIOLA P, CELANO, GIOVANNI, PSARAKIS S.   +2 more
openaire   +3 more sources

A nonparametric EWMA chart with auxiliary information for process mean

Communications in Statistics - Theory and Methods, 2018
In this paper, a new nonparametric exponentially weighted moving average (EWMA) sign chart is constructed with the help of an auxiliary-information-based (AIB) estimator of the process mean, named AIB-EWMA sign chart.
A. Haq
semanticscholar   +1 more source

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
openaire   +2 more sources

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

Ewma control chart under linear drift

Journal of Statistical Computation and Simulation, 1991
An accurate numerical procedure is presented for computing the average run length (ARL) of an exponentially weighted moving average (EWMA) chart under a linear drift in the process mean. The performance of an EWMA chart is then evaluated under a linear drift in the mean.
openaire   +1 more source

Gini's Mean Difference Based Time-Varying EWMA Charts

Economic Quality Control, 2009
The concept of time-varying control limits with reference to EWMA charts is briefly introduced and for the asymptotic control charts proposed by Riaz and Abbasi [Interstat : 3, 2007], a proposal of time-varying control limits is made. The proposed limits are subsequently compared with those of Riaz and Abbasi [Interstat : 3, 2007] asymptotic charts and
Riaz, Muhammad, Abbasi, Saddam Akber
openaire   +1 more source

A spatial rank‐based multivariate EWMA control chart

Naval Research Logistics (NRL), 2012
AbstractNonparametric control charts are useful in statistical process control 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 self‐starting methodology for monitoring location parameters. It is based on adapting the
Zou, Changliang, Wang, Zhaojun, Tsung, Fu-gee   +2 more
openaire   +3 more sources

Process adjustment when using EWMA charts

International Journal of Quality & Reliability Management, 1995
Following an alarm signal from a control chart it may be necessary to conduct an adjustment to bring the process mean towards a target value. Addresses the problem of how such an adjustment should be made, based on the use of an EWMA control chart, including the special case in which the EWMA is equivalent to the Shewhart chart. The distribution of the
openaire   +1 more source

The combined Shewhart–EWMA sign charts

Quality and Reliability Engineering International
AbstractThe Shewhart control chart is a prominent tool for identifying the changes in process parameters that are of large magnitude, however, it has reduced ability to identify the process changes of small magnitudes. On the other hand, an exponentially weighted moving average (EWMA) control chart is superior to the Shewhart chart in identifying ...
Mohammed Kadhim Shanshool, Shashibhushan B. Mahadik, Dadasaheb G. Godase, Michael B. C. Khoo   +3 more
openaire   +1 more source

Performance Comparisons of EWMA Control Chart Schemes

Quality Technology & Quantitative Management, 2010
AbstractCombining an EWMA chart with a Shewhart chart is traditionally recommended as a means of providing good protection against both small and large shifts in the process mean. Capizzi and Masarotto have proposed an EWMA chart with a variable smoothing constant (AEWMA) for the same purpose.
Simoes, Bruno F. T., Epprecht, Eugenio K., Costa, Antonio F. B.   +2 more
openaire   +1 more source