A simulation study of a discrete-time multiserver retrial queue with finite population

In this paper, we deal with a discrete-time multiserver retrial queue with finite population. Firstly, we study the Markov chain at the epochs immediately after slot boundaries making emphasis on the computation of its steady-state distribution. Then, the main performance measures are investigated. Besides, we simulate the waiting time of a customer in the retrial group under three different queueing policies. Some numerical examples are given to illustrate the analysis.     

Some theory and practical uses of trimmed L-moments

Trimmed L-moments, defined by Elamir and Seheult [2003. Trimmed L-moments. Comput. Statist. Data Anal. 43, 299–314], summarize the shape of probability distributions or data samples in a way that remains viable for heavy-tailed distributions, even those for which the mean may not exist. We derive some further theoretical results concerning trimmed L-moments: a relation with the expansion of the quantile function as a weighted sum of Jacobi polynomials; the bounds that must be satisfied by trimmed L-moments; recurrences between trimmed L-moments with different degrees of trimming; and the asymptotic distributions of sample estimators of trimmed L-moments. We also give examples of how trimmed L-moments can be used, analogously to L-moments, in the analysis of heavy-tailed data. Examples include identification of distributions using a trimmed L-moment ratio diagram, shape parameter estimation for the generalized Pareto distribution, and fitting generalized Pareto distributions to a heavy-tailed data sample of computer network traffic.     

Bayesian design in queues: An application to aeronautic maintenance

We exploit Bayesian criteria for designing M/M/c//r$M/M/c//r$ queueing systems with spares. For illustration of our approach we use a real problem from aeronautic maintenance, where the numbers of repair crews and spare planes must be sufficiently large to meet the necessary operational capacity. Bayesian guarantees for this to happen can be given using predictive or posterior distributions.     

Normal approximation to the hypergeometric distribution in nonstandard cases and a sub-Gaussian Berry–Esseen theorem

In this paper, we consider simple random sampling without replacement from a dichotomous finite population. We investigate accuracy of the Normal approximation to the Hypergeometric probabilities for a wide range of parameter values, including the nonstandard cases where the sampling fraction tends to one and where the proportion of the objects of interest in the population tends to the boundary values, zero and one. We establish a non-uniform Berry–Esseen theorem for the Hypergeometric distribution which shows that in the nonstandard cases, the rate of Normal approximation to the Hypergeometric distribution can be considerably slower than the rate of Normal approximation to the Binomial distribution. We also report results from a moderately large numerical study and provide some guidelines for using the Normal approximation to the Hypergeometric distribution in finite samples.     

Retracted and replaced: Sodium cromoglicate: an ineffective drug or meta‐analysis misused?

The following article from Pharmaceutical Statistics, Sodium cromoglicate: an ineffective drug or meta‐analysis misused? by M. T. Stevens, A. M. Edwards, J. B. L. Howell published online on 15 March 2007 in Wiley InterScience ( www.interscience.wiley.com ), has been retracted by agreement between the author, the journal Editor in Chief, Steven Julious, and John Wiley & Sons, Ltd. The retraction has been agreed because the article is not yet ready for publication and an early version without revisions was published in error. Replacement article pending. Copyright © 2007 John Wiley & Sons, Ltd.     

Physician/hospital business relationships. Sorting through the options

Providers recognize the critical role of physician/hospital partnerships in the newly emerging health care delivery system. However, the possibilities available for establishing such partnerships can be overwhelming. The authors provide a critical review of the options for physician/hospital business relationships. They emphasize the need to match physician/hospital strategies to local market characteristics, develop market-based business objectives, and structure physician/hospital relationships to support the achievement of business objectives.     

Can physicians lead other physicians into the future?

This article reflects upon some of the dynamics that prevent physicians from successfully engaging change. Physicians are enculturated to the competitive and hierarchical, and to value personal autonomy. These traits promote distrust and inhibit the formation of collaborative relationships. At this time of growing complexity, when most other industries are developing styles of work based on teamwork, worker empowerment, cross training, and information sharing, physicians cling to the metaphor of the ship's captain, a lone decision-marker and authoritarian possessor of grand knowledge. And yet, in order to lead, physicians need to learn to work differently and nurture a more collaborative approach. The author's blueprint for change includes: Stop trying to manage consensus; commit to measured accountability; think systemically; don't make the mistake of thinking that people will follow because you are right; and, most importantly, create relationships based on shared purpose and principles.     

The Zen of physician initiatives

Many physicians today feel ravaged by the brutal speed with which change has been occurring. They see the beliefs and practices of a lifetime being abandoned and replaced by the flavor of the month, management du jour. But if you are willing and able to take the brave step of approaching your physicians without an agenda, meeting with them to listen to their concerns, and can also avoid hanging a lightning-rod label on every bright new idea that comes out of the sessions, you'll be on the way to effective new management. This new style is a "Zen" approach (but don't give it that label) that lets real collaboration come into the place that is supposed to be all about healing--the health care organization. From "never call it anything" to "stay with them until they get it," ideas on how to be a Zen manager are presented, with the ultimate goal of truly partnering with physicians and infusing them with a desire to move beyond the frustration and disenchantment they are feeling.     

Making the health care delivery system accountable.

Accountability has become the fact of life for the health care provider and the delivery system. Until recently, accountability has been viewed primarily through the judicial process as issues of fraud and liability, or by managed care entities through evaluation of the financial bottom line. It is this second consideration and its ramifications that will be explored in this article. Appropriate measurement tools are needed to evaluate services, delivery, performance, customer satisfaction, and outcomes assessment. Measurement tools will be considered in light of the industry's unique considerations and realities. All participants, including insurers, employers, management, and health care providers and recipients, bear responsibilities which necessitate assessment and analysis. However, until the basic question, "Who is the customer?" is resolved, accountability issues remain complex and obscured. Accountability costs and impacts must be evaluated over time. They go way beyond bottom line cost containment and reduction. Accountability will be accomplished when the health care industry implements quality and measurement concepts that yield the highest levels of validity and appropriateness for health care delivery.