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A EWMA control chart based on an auxiliary variable and repetitive sampling for monitoring process location |
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| Authors: | Aamir Saghir Liaquat Ahmad Chi-Hyuck Jun |
| Affiliation: | 1. Department of Mathematics, Mirpur University of Science and Technology (MUST), Mirpur (AJK), Pakistan;2. Department of Statistics and computer Science, University of Veterinary and Animal Sciences, Mirpur, Lahore, Pakistan;3. Department of Industrial and Management Engineering, POSTECH, Pohang, Republic of Korea |
| Abstract: | ABSTRACTThis article develops an exponentially weighted moving average (EWMA) control chart using an auxiliary variable and repetitive sampling for efficient detection of small to moderate shifts in location. A EWMA statistic of a product estimator of the average (which utilities the information of auxiliary variables as well as repetitive sampling) is plotted on the proposed chart. The control chart coefficients of the proposed EWMA chart are determined for two strategic limits known as outer and inner control limits for the target in-control average run length. The performance of the proposed EWMA chart is studied using average run length when a shift occurs in the process average. The efficiency of the developed chart is compared with the competitive existing control charts. The results of the study revealed that proposed EWMA chart is more efficient than others to detect small changes in process mean. |
| Keywords: | Auxiliary information EWMA process mean Repetitive group sampling Average run length |