Re-weighted Robust Control Charts for Individual Observations
نویسندگان
چکیده
Control chart is the most valuable tool in statistical process control (SPC) and it is used to monitor the changes in a process. It presents a graphical display of process stability or instability over time. This enable us to instantly understand, whether the process is under control or not. Hotelling’s T 2 chart is one of the most popular control charts for monitoring independently and identically distributed random vectors. In the computation of Hotelling’s T , the classical mean and covariance are utilized, hence the results can be heavily influenced by outliers. In order to decrease the impact of outliers we propose to use the re-weighted robust estimator instead of the classical estimator in the computation of Hotelling’s T . In this paper we construct a new statistic by substituting the classical estimators in Hotelling’s T 2 by the reweighted MCD.
منابع مشابه
Control chart based on residues: Is a good methodology to detect outliers?
The purpose of this article is to evaluate the application of forecasting models along with the use of residual control charts to assess production processes whose samples have autocorrelation characteristics. The main objective is to determine the efficiency of control charts for individual observations (CCIO) and exponentially weighted moving average (EWMA) charts when they are applied to res...
متن کاملRobust economic-statistical design of the EWMA-R control charts for phase II linear profile monitoring
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 ...
متن کاملNew control charts for monitoring covariance matrix with individual observations
It has recently been shown that the performance of multivariate exponentially weighted mean square (MEWMS) and multivariate exponentially weighted moving variance (MEWMV) charts of Huwang et al. (2007) in monitoring the variability of a multivariate process for individual observations is better than existing schemes. Both of these control charts monitor a distinct matrix which is an estimator o...
متن کاملThe Robustness of the Multivariate EWMA Control Chart
Control charts are graphical tools widely used to monitor manufacturing processes to quickly detect any change in a process that may result in a change in product quality. The statistic plotted on a control chart is based on samples of n ≥ 1 observations (rational subgroups) that may be taken at regular sampling intervals. However, there are numerous practical applications using individual obse...
متن کاملThe Max EWMAMS control chart for joint monitoring of process mean and variance with individual observations
A traditional approach to monitor both the location and the scale parameters of a quality characteristic is to use two separate control charts. These schemes have some difficulties in concurrent tracking and interpretation. To overcome these difficulties, some researchers have proposed schemes consisting only one chart. However, none of these schemes is designed to work with individual observat...
متن کامل