References of "Seif, A"
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See detailA Statistically adaptive sampling policy to the Hotelling's T2 Control Chart: Markov Chain Approach
Seif, A.; Faraz, Alireza ULg; Heuchenne, Cédric ULg et al

in Communications in Statistics : Theory & Methods (2014)

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See detailA Meta Model to Optimally Design the VSI T2 Control Chart
Faraz, Alireza ULg; Seif, A.

in international Journal of Applied Operational Research (2012), 1(3), 53-69

Recent studies have shown that the variable sampling interval (VSI) scheme helps practitioners to detect process shifts more quickly than the classical scheme (FRS). In this paper, the economically and ... [more ▼]

Recent studies have shown that the variable sampling interval (VSI) scheme helps practitioners to detect process shifts more quickly than the classical scheme (FRS). In this paper, the economically and statistically optimal design of the VSI T2 control chart for monitoring the process mean vector is investigated. The cost model proposed by Lorenzen and Vance [1] based on the Markov chain approach is modified as the objective function which is intended to be minimized through a genetic algorithm (GA) approach. Then, the effects of the costs and operating parameters on the optimal design (OD) of the chart parameters; and resulting operating loss through a fractional factorial design is systematically studied and finally, based on the ANOVA results, a Meta model to facilitate implementation in industry is proposed to determine the OD of the VSI T2 control chart parameters from the process and cost parameters. [less ▲]

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See detailA modified economic-statistical design of the T2 control chart with variable sample sizes and control limits
Seif, A.; Faraz, Alireza ULg; Heuchenne, Cédric ULg et al

in Journal of Applied Statistics (2011), 38(11), 2459-2469

Recent studies have shown that using variable sampling size and control limits (VSSC) schemes result in charts with more statistical power than variable sampling size (VSS) when detecting small to ... [more ▼]

Recent studies have shown that using variable sampling size and control limits (VSSC) schemes result in charts with more statistical power than variable sampling size (VSS) when detecting small to moderate shifts in the process mean vector. This paper presents an economic-statistical design (ESD) of the VSSC T2 control chart using the general model of Lorenzen and Vance [22]. The genetic algorithm approach is then employed to search for the optimal values of the six test parameters of the chart. We then compare the expected cost per unit of time of the optimally designed VSSC chart with optimally designed VSS and FRS (fixed ratio sampling) T2 charts as well as MEWMA charts. [less ▲]

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See detailStatistical design of the Hotelling’s T2 control chart with variable ratio sampling scheme using genetic algorithms
Torabian, M.; Faraz, Alireza ULg; Seif, A.

in Journal of Applied Mathematics (2009), 6(22), 77-89

The familiar multivariate process monitoring and control procedure is the Hotelling’s T2 control chart, a direct analog of the univariate shewhart chart. But, its efficiency for detecting small to ... [more ▼]

The familiar multivariate process monitoring and control procedure is the Hotelling’s T2 control chart, a direct analog of the univariate shewhart chart. But, its efficiency for detecting small to moderate shifts in the process mean is poor. To improve the power of chart, this paper studies the statistical design of the T2 chart with variable ratio sampling scheme. It is assumed that the length of time the process remains in control has exponential distribution. The chart is modeled using Markov chains and is optimized using genetic algorithm optimization method. The results show that the T2 chart with variable ratio sampling scheme is quicker than the classical one in detecting almost all shifts in the process mean. [less ▲]

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See detailImproving the power of out of control states detection in multivariate processes using variable sampling intervals policy
Seif, A.; Faraz, Alireza ULg; Torabian, M.

in Journal of Applied Mathematics (2009), 23

The familiar multivariate process monitoring and control procedure is the Hotelling’s T2 control chart, a direct analog of the univariate shewhart chart. But, its efficiency for detecting small to ... [more ▼]

The familiar multivariate process monitoring and control procedure is the Hotelling’s T2 control chart, a direct analog of the univariate shewhart chart. But, its efficiency for detecting small to moderate shifts in the process mean is poor. To improve the power of chart, this paper presents the variable sampling intervals (VSI) scheme. It is assumed that the length of time the process remains in control has exponential distribution. The chart is modeled using Markov chains and is optimized using genetic algorithm optimization method. The results show that the T2 chart with variable ratio sampling scheme is quicker than the classical one in detecting almost all shifts in the process mean [less ▲]

Detailed reference viewed: 21 (4 ULg)