References of "Faraz, Alireza"
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See detailOptimal T2 control chart with double sampling scheme - an alternative to the MEWMA chart
Faraz, Alireza ULg; Heuchenne, Cédric ULg; Saniga, Erwin

in Quality and Reliability Engineering International (2012), 28(7), 751-760

Recent studies have shown that the double sampling (DS) scheme yields rapid detection of out of control situations, but the economic consequences of applying the proposed method are not discussed in the ... [more ▼]

Recent studies have shown that the double sampling (DS) scheme yields rapid detection of out of control situations, but the economic consequences of applying the proposed method are not discussed in the literature yet. In this paper, the economic statistical design of the DS T2 control chart is designed to address this issue. In this regard, upon the Lorenzen and Vance (1986)’s economic model, the problem is formulized and then the cost function is minimized using the genetic algorithm search method to obtain the optimal design parameters. Besides, we assumed that the length of the time that process remains in control is exponentially distributed. Through an illustrative example we show that by applying the proposed method relatively large benefits can be achieved in a comparison with the classical T2 and the statistical DS T2 charts. Furthermore the performance of the ESD DS T2 charts is compared to the MEWMA and other variable ratio sampling (VRS) T2 control charts in the literature. [less ▲]

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See detailA modified economic-statistical design of the VP multivariate control charts
SEIF, Asghar; Faraz, Alireza ULg

Conference (2012, January 15)

Hotelling’s T2 control chart is one of the most popular multivariate control charts for monitoring multiple variables simultaneously. Recent studies have shown that applying the T2 control chart by using ... [more ▼]

Hotelling’s T2 control chart is one of the most popular multivariate control charts for monitoring multiple variables simultaneously. Recent studies have shown that applying the T2 control chart by using a variable parameters (VP) scheme yields more rapid detection of assignable causes than the classical method of taking fixed sample sizes at fixed intervals of time. This paper presents an economic-statistical design (ESD) of the VP T2 control chart using the general model of Lorenzen and Vance. The genetic algorithm (GA) is then employed to search for the optimal values of the eight test parameters of the chart. Furthermore, VP and FRS schemes are compared with respect to the expect cost per unit time. [less ▲]

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See detailOn the advantages of economically designed the Hotelling’s T2 control chart with variable sample sizes and sampling intervals
Faraz, Alireza ULg; kazemzadeh, R. B.; Parsian, Ahmad 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 ▲]

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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 detailEconomic Design of Control Charts In Presence of Censored Data
Faraz, Alireza ULg; Heuchenne, Cédric ULg

Speech/Talk (2011)

we present Shewhart type Z ̅ and S2 control charts for monitoring individual or joint shifts in the scale and shape parameters of a Weibull distributed process. The advantage of this method is its ease of ... [more ▼]

we present Shewhart type Z ̅ and S2 control charts for monitoring individual or joint shifts in the scale and shape parameters of a Weibull distributed process. The advantage of this method is its ease of use and flexibility for the case where the process distribution is Weibull, although the method can be applied to any distribution. We illustrate the performance of our method through simulation and the application through the use of an actual data set. Our results indicate that Z ̅ and S2 control charts perform well in detecting shifts in the scale and shape parameters. We also provide a guide that would enable a user to interpret out-of-control signals. [less ▲]

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See detailThe Economic and Statistical Designs of Control charts for Censored and Non-Normal Data
Faraz, Alireza ULg; Heuchenne, Cédric ULg; Davis, Darwin, Edward et al

Scientific conference (2011, December)

In this research, we are dealing with constructing the statistical design (SD) and economic statistical design (ESD) of Shewhart and CUSUM control charts for reliability data which are right censored ... [more ▼]

In this research, we are dealing with constructing the statistical design (SD) and economic statistical design (ESD) of Shewhart and CUSUM control charts for reliability data which are right censored. This is the case which happens more frequently in the field. [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 Merits and Economic Evaluation of T2 Control Charts with the VSSC Scheme
Seif, Asghar; Moghadam, M.B.; Faraz, Alireza ULg et al

in Arabian Journal for Science and Engineering (2011), 36(7), 1461-1470

T2 control charts are used to monitor a process when more than one quality variable associated with the process is being observed. Recent studies have shown that using variable sampling size (VSS) schemes ... [more ▼]

T2 control charts are used to monitor a process when more than one quality variable associated with the process is being observed. Recent studies have shown that using variable sampling size (VSS) schemes results in charts with more statistical power for detecting small to moderate shifts in the process mean vector. This paper presents an economic-statistical design of T2 control charts with variable sample size and control limits (VSSC). We build a cost model of a VSSC T2 control chart for the purpose of economic-statistical design using the model of Costa and Rahim (J. Appl. Stat. 28:875–885, 2001). This cost model constructed involves the cost of false alarms, the cost of finding and eliminating an assignable cause, the cost associated with production in an out-of-control state, and the cost of sampling and testing. We optimize this model using a genetic algorithm approach. Furthermore, VSSC and VSS T2 charts are compared with respect to the expected cost per unit time. [less ▲]

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See detailA unification and some corrections to Markov chain approaches to develop variable ratio sampling scheme control charts
Faraz, Alireza ULg; Saniga, Erwin

in Statistical Papers (2011), 52(4), 799-811

We provide some unifying definitions, make some corrections to articles by Faraz and Parsian (J Stat Pap 47:569–593, 2006) and Costa (JQual Technol 26:155– 163, 1994; 29:197–204, 1997), and using these ... [more ▼]

We provide some unifying definitions, make some corrections to articles by Faraz and Parsian (J Stat Pap 47:569–593, 2006) and Costa (JQual Technol 26:155– 163, 1994; 29:197–204, 1997), and using these provide more accurate tables of results and comparisons of control charts. We also investigate the impact of an incorrectly specified process shift on signal frequency. [less ▲]

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See detailMULTIOBJECTIVE DESIGN OF CONTROL CHARTS
Faraz, Alireza ULg; Heuchenne, Cédric ULg

Conference (2011, September 24)

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See detailMonitoring delivery chains in a supply chain using multivariate control charts
Faraz, Alireza ULg; Heuchenne, Cédric ULg; Saniga, Erwin et al

Conference (2011, July 13)

The theory of the delivery chain considers the delivery of goods and services to customers within a specific time interval. Nowadays, organizations are focusing to satisfy their customers’ demands not ... [more ▼]

The theory of the delivery chain considers the delivery of goods and services to customers within a specific time interval. Nowadays, organizations are focusing to satisfy their customers’ demands not only to meet the expectations for products quality but also in delivery times through managing delivery chains. Obviously it is desirable that a company has minimum delivery time of goods and services to its customers. Therefore, establishing economic and reliable control charts for monitoring the key characteristics of delivery chain is of great importance especially for managers to improve the whole delivery chains performance. On the other hand, as we shall see in the present paper, the performance of a delivery chain is multivariate in nature because customers do not evaluate a delivery performance with a univariate mindset and also there are usually several production and delivery sites, and variety of different methods of transportation of goods and services. In this paper, we propose a relatively new application of the economic statistical design of the multivariate T2 control chart to monitor the delivery chain performance and it is illustrated through a case study in the TNT express mail in Iran. [less ▲]

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See detailOn the properties of the hotelling’s T2 control chart with variable sampling intervals
Faraz, Alireza ULg; Chalaki, Kamyar; Moghadam, M. B.

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 ▲]

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See detailEconomic Statistical Design of a T2 Control Chart with Double Warning Lines
Faraz, Alireza ULg; Saniga, Erwin

in Quality and Reliability Engineering International (2011), 27(2), 125-139

Recent studies have shown that enhancing the common T2 control chart by using variable sample sizes (VSS) and variable sample intervals (VSI) sampling policies with a double warning line scheme (DWL ... [more ▼]

Recent studies have shown that enhancing the common T2 control chart by using variable sample sizes (VSS) and variable sample intervals (VSI) sampling policies with a double warning line scheme (DWL) yields improvements in shift detection times over either pure VSI or VSS schemes in detecting almost all shifts in the process mean. In this paper, we look at this problem from an economical perspective, certainly at least as an important criterion as shift detection time if one considers what occurs in the industry today. Our method is to first construct a cost model to find the economic statistical design (ESD) of the DWL T2 control chart using the general model of Lorenzen and Vance (Technometrics 1986; 28:3–11). Subsequently, we find the values of the chart parameters which minimize the cost model using a genetic algorithm optimization method. Cost comparisons of Fixed ratio sampling, VSI, VSS, VSIVSS with DWL, and multivariate exponentially weighted moving average (MEWMA) charts are made, which indicate the economic efficacy of using either VSIVSS with DWL or MEWMA charts in practice if cost minimization is of interest to the control chart user. [less ▲]

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See detailEconomic and Economical Statistical Design of Hotelling’s T2 Control Chart with Two-State Adaptive Sample Size
Faraz, Alireza ULg; Saniga, Erwin; kazemzadeh, R. B.

in Journal of Statistical Computation & Simulation (2010), 80(12), 12991316

The Hotelling’s T 2 control chart, a direct analogue of the univariate Shewhart ¯X chart, is perhaps the most commonly used tool in industry for simultaneous monitoring of several quality characteristics ... [more ▼]

The Hotelling’s T 2 control chart, a direct analogue of the univariate Shewhart ¯X chart, is perhaps the most commonly used tool in industry for simultaneous monitoring of several quality characteristics. Recent studies have shown that using variable sampling size (VSS) schemes results in charts with more statistical power when detecting small to moderate shifts in the process mean vector. In this paper, we build a cost model of a VSS T 2 control chart for the economic and economic statistical design using the general model of Lorenzen and Vance [The economic design of control charts: A unified approach, Technometrics 28 (1986), pp. 3–11].We optimize this model using a genetic algorithm approach.We also study the effects of the costs and operating parameters on theVSS T 2 parameters, and show, through an example, the advantage of economic design over statistical design forVSS T 2 charts, and measure the economic advantage of VSS sampling versus fixed sample size sampling. [less ▲]

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See detailECONOMICALLY DESIGNED HOTELLING’S T2 CONTROL CHART USING VSICL SCHEME
torabian, Mohsen; Moghadam, M. B.; Faraz, Alireza ULg

in Arabian Journal for Science & Engineering (2010), 35(2), 251263

The Hotelling’s T2 control chart, is the most widely used multivariate procedure for two or more related quality characteristics, but it’s power lacks the desired performance in detecting small to ... [more ▼]

The Hotelling’s T2 control chart, is the most widely used multivariate procedure for two or more related quality characteristics, but it’s power lacks the desired performance in detecting small to moderate shifts. Recently, the variable sampling intervals (VSI) control scheme in which the length of successive sampling intervals is determined upon the preceding T2 values has been proved to have a very good performance on detecting small to moderate shifts when it is compared to the original T2 control chart . Moreover, it has been shown that the VSI scheme is more economical than the classical one. This paper studies the economic consequences of a new control scheme named variable sampling intervals and control limits (VSICL) in that the sampling interval h and control limit k vary between minimum and maximum values while keeping the sample size fixed over time. We apply the cost model proposed by Costa and Rahim [8]. Furthermore, we assume that the length of time that the process remains in control is exponentially distributed which allows us to apply the Markov chain approach for developing the cost model. We apply genetic algorithm to determine the optimal values of model parameters by minimizing the cost function. Finally, both VSI and VSICL T2 control charts are compared with respect to the expected cost per unit time. [less ▲]

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See detailAn application of fuzzy random variables to control charts
Faraz, Alireza ULg; Shapirob, Arnold

in Fuzzy Sets & Systems (2010), 161(20), 26842694

The two most significant sources of uncertainty are randomness and incomplete information. In real systems, we wish to monitor processes in the presence of these two kinds of uncertainty. This paper aims ... [more ▼]

The two most significant sources of uncertainty are randomness and incomplete information. In real systems, we wish to monitor processes in the presence of these two kinds of uncertainty. This paper aims to construct a fuzzy statistical control chart that can explain existing fuzziness in data while considering the essential variability between observations. The proposed control chart is an extension of Shewhart ¯X − S2 control charts in fuzzy space. The proposed control chart avoids defuzzification methods such as fuzzy mean, fuzzy mode, fuzzy midrange, and fuzzy median. It is well known that using different representative values may cause different conclusions to be drawn about the process and vague observations to be reduced to exact numbers, thereby reducing the informational content of the original fuzzy sets. The out-of-control states are determined based on a fuzzy in-control region and a simple and precise graded exclusion measure that determines the degree to which fuzzy subgroups are excluded from the fuzzy in-control region. The proposed chart is illustrated with a numerical example. [less ▲]

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See detailConstructing a fuzzy Shewhart control chart for variables when uncertainty and randomness are combined
Faraz, Alireza ULg; Kazemzadeh, R. B.; Moghadam, M. B. 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 ▲]

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See detailStatistical process control and delivery chains
Faraz, Alireza ULg; Kazemzadeh, R.B.

in International Journal of Industrial Engineering & Production Research (2010), 21(3), 55-66

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See detailThe Optimal Design of the VSI T2 Control Chart
Faraz, Alireza ULg; Kazemzadeh, R. B.; Heuchenne, Cédric ULg et al

in Journal of Iranian Statistical Society (2010), 9(1), 1-19

Recent studies have shown that the variable sampling interval (VSI) scheme helps practitioners 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 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 (1986) is 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 ▲]

Detailed reference viewed: 46 (9 ULg)
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See detailA Meta Model to Optimal Design the VSI T2 Chart
Faraz, Alireza ULg; Heuchenne, Cédric ULg; Saniga, E.

Report (2010)

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