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On the advantages of economically designed the Hotelling’s T2 control chart with variable sample sizes and sampling intervals Faraz, Alireza ; ; et al in Quality & Quantity (2012), 46(1), 39-53 Faraz and Parsian (Statistical Paper, 47: 569–593, 2006) have shown that the double warning lines (DWL) scheme detects process shifts more quickly than the other variable ratio sampling schemes such as ... [more ▼] Faraz and Parsian (Statistical Paper, 47: 569–593, 2006) have shown that the double warning lines (DWL) scheme detects process shifts more quickly than the other variable ratio sampling schemes such as variable sample sizes (VSS), variable sampling intervals (VSI) and variable sample sizes and sampling intervals (VSSVSI). In this paper, the DWLT2control chart for monitoring the process mean vector is economically designed. The cost model proposed by Costa and Rahim (Journal of Applied Statistics, 28: 875–885, 2001) is used here and is minimized through a genetic algorithm (GA) approach. Then the effects of the model parameters on the chart parameters and resulting operating loss is studied and finally a comparison between all possible variable ratio sampling (VRS) schemes are made to choose the best option economically. [less ▲] Detailed reference viewed: 60 (16 ULg)On the properties of the hotelling’s T2 control chart with variable sampling intervals Faraz, Alireza ; ; in Quality & Quantity (2011), 45(3), 579-586 When T 2 control chart is used to monitor a process, it is usually assumed that the samples of size n0 is taken at constant intervals t0 . In this paper, we investigate the T 2 control chart for ... [more ▼] When T 2 control chart is used to monitor a process, it is usually assumed that the samples of size n0 is taken at constant intervals t0 . In this paper, we investigate the T 2 control chart for monitoring the process mean vector when the sampling intervals are variable. Recent studies have shown that the variable sampling interval (VSI) scheme helps practitioners detect process shifts more quickly than the classical scheme Fixed Ratio Sampling (FRS). In this paper, it is assumed that the length of time the process remains in control is exponentially distributed. [less ▲] Detailed reference viewed: 42 (7 ULg)Constructing a fuzzy Shewhart control chart for variables when uncertainty and randomness are combined Faraz, Alireza ; ; et al in Quality & Quantity (2010), 44(5), 905-914 In this paper we introduce a fuzzy chart for variables which is used in situations when uncertainty and randomness are combined. It is showed that the Shewhart chart’s control limits must be adjusted in ... [more ▼] In this paper we introduce a fuzzy chart for variables which is used in situations when uncertainty and randomness are combined. It is showed that the Shewhart chart’s control limits must be adjusted in these situations. However, this chart is based on a fuzzy acceptance region and this method arises when a decision should be made by referring to the grade of a sample statistic belonging to the fuzzy acceptance region. [less ▲] Detailed reference viewed: 56 (6 ULg)Hotelling’s T2 control chart with two adaptive sample sizes Faraz, Alireza ; in Quality & Quantity (2009), 43(6), 903-913 Some quality control schemes have been developed when several related quality characteristics are to be monitored. The familiar multivariate process monitoring and control procedure is the Hotelling’s T 2 ... [more ▼] Some quality control schemes have been developed when several related quality characteristics are to be monitored. The familiar multivariate process monitoring and control procedure is the Hotelling’s T 2 control chart for monitoring the mean vector of the process. It is a direct analog of the univariate shewhart ¯ x chart. As in the case of univariate, the ARL improvements are very important particularly for small process shifts. In this paper, we study the T 2 control chart with two-state adaptive sample size, when the shift in the process mean does not occur at the beginning but at some random time in the future. Further, the occurrence time of the shift is assumed to be exponentially distributed random variable. [less ▲] Detailed reference viewed: 71 (5 ULg)Hotelling’s T 2 control chart with two adaptive sample sizes Faraz, Alireza ; in Quality & Quantity (2009), 43 Some quality control schemes have been developed when several related quality characteristics are to be monitored. The familiar multivariate process monitoring and control procedure is the Hotelling’s T 2 ... [more ▼] Some quality control schemes have been developed when several related quality characteristics are to be monitored. The familiar multivariate process monitoring and control procedure is the Hotelling’s T 2 control chart for monitoring the mean vector of the process. It is a direct analog of the univariate shewhart ¯ x chart. As in the case of univariate, the ARL improvements are very important particularly for small process shifts. In this paper, we study the T 2 control chart with two-state adaptive sample size, when the shift in the process mean does not occur at the beginning but at some random time in the future. Further, the occurrence time of the shift is assumed to be exponentially distributed random variable. [less ▲] Detailed reference viewed: 25 (4 ULg)Fuzzy Control Chart A Better Alternative for Shewhart Average Chart Faraz, Alireza ; in Quality & Quantity (2007), 41(3), 375-385 This paper through a real illustrative example and a power test shows that designing a fuzzy control chart for process average of a continuous (variable) quality characteristic with a warning line is a ... [more ▼] This paper through a real illustrative example and a power test shows that designing a fuzzy control chart for process average of a continuous (variable) quality characteristic with a warning line is a better alternative to Shewhart ¯X chart in many respects, like providing better neural view to inspectors, offering different strategic options for company to choose, detecting the desire shifts more quickly, and more sensibility to small shifts without any complexity augmentation to the chart. [less ▲] Detailed reference viewed: 67 (10 ULg) |
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