Amjad D. Al-Nasser

Evaluating functional relationship between image, customer satisfaction and customer loyalty using general maximum entropy

Much has been written in the past few years on customer satisfaction. Traditional approaches to customer satisfaction, however, have been too narrow in scope in the way satisfaction is measured. Most instruments to measure customer satisfaction are not sensitive to the fact that a customer’s voice has a wide spectrum and goes beyond the single note of satisfaction or happiness. Most approaches fail to link customer satisfaction to drivers of loyalty and market share and to processes that contribute to pro® tability. Traditional approaches to customer satisfaction also do not oVer a comprehensive way to measure the range of perceptions that in ̄ uence customer behaviour. Organizations that want to improve quality signi® cantly by aligning internal processes to the voice of the customer must look beyond customer satisfaction to market-oriented measures for gauging progress. This requires shifting attention away from customer satisfaction to the more comprehensive concept of customer loyalty. Loyal customers stick with their suppliers or service providers over the long run. They also express their loyalty by giving a greater share of their wallets to their high-value brands or service providers and by generating word-of-mouth referrals. All of these behaviours will directly aVect pro® tability. But it takes a lot more than customer satisfaction to make a customer loyal and to make internal processes truly responsive to customer needs, market share opportunities and pro® t objectives. Recent studies have demonstrated mixed results in analysing the relationship between satisfaction and loyalty. Several studies have indeed found satisfaction to be a (and often the) leading factor in determining loyalty (e.g. Anderson & Fornell, 1994; Oliver & Linda, 1981; Pritchard, 1991). Other studies, however, suggest satis® ed customers may not be suYcient to create loyal customers (e.g. Cronin & Taylor, 1992; Fornell, 1992; Oliva et al., 1992). These studies tend to support Reichheld’s (1993) argument that customer satisfaction is not a surrogate for customer loyalty, and thus increasing customer satisfaction does not necessarily lead to increased customer loyalty to a product, service or organization. To gain further insight into the development of customer loyalty toward a service or product, this study looks

L Ranked Set Sampling: A Generalization Procedure for Robust Visual Sampling

In this article, a robust ranked set sampling (LRSS) scheme for estimating population mean is introduced. The proposed method is a generalization for many types of ranked set sampling that introduced in the literature for estimating the population mean. It is shown that the LRSS method gives unbiased estimator for the population mean with minimum variance providing that the underlying distribution is symmetric. However, for skewed distributions a weighted mean is given, where the optimal weights is computed by using Shannons entropy. The performance of the population mean estimator is discussed along with its properties. Monte Carlo comparisons for detecting outliers are made with the traditional simple random sample and the ranked set sampling for some distributions. The results indicate that the LRSS estimator is superior alternative to the existing methods.

Comparing generalised maximum entropy and partial least squares methods for structural equation models

The generalised maximum entropy (GME) method is presented for estimating structural equation models, where a real data set of the Service & Motor Vehicle Industry in Sweden is used to show the implementation of the method. Monte Carlo simulation comparisons are also made between GME and partial least squares (PLS) methods in the presence of messy data. Three cases are considered: outliers, missing data and multicollinearity. It is shown that this method can be considered a valid alternative to the conventional method of PLS, where the results of GME, in terms of mean squared error, outperform the PLS results in some respects.

Methylenetetrahydrofolate Reductase Polymorphisms C677T and A1298C as Maternal Risk Factors for Down Syndrome in Jordan

BACKGROUND The activity of the methylenetetrahydrofolate reductase (MTHFR) enzyme is regulated by the two polymorphisms C677T and A1298C, which reduce enzyme activity and result in hypomethylation of chromosomes that increase the risk of nondisjunction. These polymorphisms are suggested to be risk factors for Down syndrome (DS) in some populations. AIM The aim of this study was to test if C677T and A1298C polymorphisms are correlated to maternal risk of DS in Jordan. METHODS The proportions of C677T and A1298C polymorphisms were examined in 53 case mothers who delivered DS children and 29 controls. The median age of case mothers was 35 years when delivering their affected children. Polymerase chain reaction-restriction fragment length polymorphism was used for genotyping. RESULTS The frequency of MTHFR C677T allele in all DS mothers was 3.2-fold higher than in the controls (odds ratio [OR] = 3.12, 95% confidence interval [CI]: 1.303-7.677). Also, the proportion of 677T in the older case mothers was different from the controls, but was significantly higher in younger case mothers than in the controls (OR = 4.2, 95% CI: 1.61-10.97, p = 0.003). The proportions of 677CT and 677TT genotypes in younger cases are, respectively, 10- and 9-fold higher than in the controls. The proportions of MTHFR A1298C are significantly different among all case groups and the controls (χ(2) = 4.27, p = 0.127), but there was a significant difference between young case mothers and both older case mothers group and the controls (OR = 1.25, 95% CI: 0.405-3.85, p = 0.698). CONCLUSIONS There is strong association between MTHFRC677T and maternal risk of DS in Jordanian mothers younger than 35 years old and the MTHFR1298C allele has a lesser but additive risk effect in MTHFR677T/1298C compound heterozygotes.

Acceptance sampling plan based on truncated life tests for exponentiated fréchet distribution

Abstract In this paper, exponentiated Fréchet distribution is considered as a model for a life time random variable when the life test is truncated at a pre-assigned time. The operating characteristic functions values of the suggested sampling plans and the corresponding producers risk are obtained.

Robust extreme ranked set sampling

In this paper, a robust extreme ranked set sampling (RERSS) procedure for estimating the population mean is introduced. It is shown that the proposed method gives an unbiased estimator with smaller variance, provided the underlying distribution is symmetric. However, for asymmetric distributions a weighted mean is given, where the optimal weights are computed by using Shannons entropy. The performance of the population mean estimator is discussed along with its properties. Monte Carlo simulations are used to demonstrate the performance of the RERSS estimator relative to the simple random sample (SRS), ranked set sampling (RSS) and extreme ranked set sampling (ERSS) estimators. The results indicate that the proposed estimator is more efficient than the estimators based on the traditional sampling methods.

On MxG1G21 queue with optional re-service

We study a single server queue with batch arrivals and two types of heterogeneous service with different general (arbitrary) service time distributions. The server provides either type of service to customers, one by one, on a first come, first served basis. Just before a service starts, a customer has the option to choose either type of service after completion of which the customer may leave the system or may opt for re-service of the service taken by him. We obtain steady-state results in explicit and closed form in terms of the probability generating functions for the number of customers in the queue and the system, the average number of customers and the average waiting time in the queue as well as the system. Some special cases of interest are discussed and some known results have been derived. A numerical illustration is provided.

Statistical Quality Control Limits for the Sample Mean Chart Using Robust Extreme Ranked Set Sampling

Abstract In this paper, new quality control charts for the mean are considered using robust extreme ranked set sampling (RERSS) method. The new charts are compared with the classical control charts using simple random sampling (SRS) and ranked set sampling methods (RSS). It is found that the RERSS charts perform better than all other charts based on SRS and RSS methods in terms of their average run length (ARL).

On Mx/(G1G2)/1/G(BS)/Vs vacation queue with two types ofgeneral heterogeneous service

We analyze a batch arrival queue with a single server providing two kinds of general heterogeneous service. Just before his service starts, a customer may choose one of the services and as soon as a service (of any kind) gets completed, the server may take a vacation or may continue staying in the system. The vacation times are assumed to be general and the server vacations are based on Bernoulli schedules under a single vacation policy. We obtain explicit queue size distribution at a random epoch as well as at a departure epoch and also the mean busy period of the server under the steady state. In addition, some important performance measures such as the expected queue size and the expected waiting time of a customer are obtained. Further, some interesting particular cases are also discussed.

Smoking‐cessation practice guidelines: awareness and implementation among medical teams

Objectives The aim was to evaluate the awareness and implementation of the Smoking Cessation Clinical Practice (SCCP) guidelines.