Reliability characteristics of Farlie–Gumbel–Morgenstern family of bivariate distributions

Abstract

In this paper, we study the Farlie–Gumbel–Morgenstern family of bivariate distributions from a reliability point of view. The properties of this family of distributions and the association between the two variables are investigated by studying the local dependence function and the association measure defined by Clayton (1978 Clayton, D.G. (1978). A model for association in bivariate life tables and its applications in epidemiological studies of familial tendency in chronic disease incidence. Biometrika 65:141–151.[Crossref], [Web of Science ®] , [Google Scholar]). We also study the effect of the association parameter on the hazard components, the failure rate of the series system, and the regression mean residual life of a parallel system. Stochastic comparisons with respect to the association parameter are also studied. Some examples are provided to illustrate the results.     

The role of weighted distributions in stochastic modeling

C. R. Rao pointed out that “The role of statistical methodology is to extract the relevant information from a given sample to answer specific questions about the parent population” and raised the question “What population does a sample represent”? Wrong specification can lead to invalid inference giving rise to a third kind of error. Rao introduced the concept of weighted distributions as a method of adjustment applicable to many situations.

In this paper, we study the relationship between the weighted distributions and the parent distributions in the context of reliability and life testing. These relationships depend on the nature of the weight function and give rise to interesting connections between the different ageing criteria of the two distributions. As special cases, the length biased distribution, the equilibrium distribution of the backward and forward recurrence times and the residual life distribution, which frequently arise in practice, are studied and their relationships with the original distribution are examined. Their survival functions, failure rates and mean residual life functions are compared and some characterization results are established.     

Simple Approximation Algorithms for MAXNAESP and Hypergraph 2-colorability

Hypergraph 2-colorability, also known as set splitting, is a widely studied problem in graph theory. In this paper we study the maximization version of the same. We recast the problem as a special type of satisfiability problem and give approximation algorithms for it. Our results are valid for hypergraph 2-colorability, set splitting and MAX-CUT (which is a special case of hypergraph 2-colorability) because the reductions are approximation preserving. Here we study the MAXNAESP problem, the optimal solution to which is a truth assignment of the literals that maximizes the number of clauses satisfied. As a main result of the paper, we show that any locally optimal solution (a solution is locally optimal if its value cannot be increased by complementing assignments to literals and pairs of literals) is guaranteed a performance ratio of . This is an improvement over the ratio of attributed to another local improvement heuristic for MAX-CUT (C. Papadimitriou, Computational Complexity, Addison Wesley, 1994). In fact we provide a bound of for this problem, where k 3 is the minimum number of literals in a clause. Such locally optimal algorithms appear to subsume typical greedy algorithms that have been suggested for problems in the general domain of satisfiability. It should be noted that the NAESP problem where each clause has exactly two literals, is equivalent to MAX-CUT. However, obtaining good approximation ratios using semi-definite programming techniques (M. Goemans and D.P. Williamson, in Proceedings of the 26th Annual ACM Symposium on Theory of Computing, 1994a, pp. 422–431) appears difficult. Also, the randomized rounding algorithm as well as the simple randomized algorithm both (M. Goemans and D.P. Williamson, SIAM J. Disc. Math, vol. 7, pp. 656–666, 1994b) yield a bound of for the MAXNAESP problem. In contrast to this, the algorithm proposed in this paper obtains a bound of for this problem.     

Multivariate discrete reversed hazard rates

In the present paper, we define and study four versions of multivariate discrete reversed hazard rates, namely scalar reversed hazard rate, vector reversed hazard rate, alternative reversed hazard rate, and conditional reversed hazard rate. Various properties of these functions are studied. Interrelationships between these reversed hazard rates are explored. We also present characterization of discrete distributions using these reversed hazard rates.     

INFLUENCE OF POWER BASES IN ORGANIZATIONAL DECISION MAKING: A CONTINGENCY MODEL*

The relative influence of four power bases was investigated in four decision-making contexts using data from forty successfully implemented decisions. The analysis suggests that position power decreases in influence while resource power and political power increase in influence as decision contexts vary from less to more uncertainty. Expert power derives its influence when organizational uncertainty is low and when technical uncertainty is reduced, whereas political power thrives when organizational uncertainty is high and when technical uncertainty remains high. Indexing the influence of power bases provides greater understanding of decision processes than the sociological or social-psychological approaches of studying participation.     

Antipolitics and Counterpolitics in Nepal’s Civil Society: The Case of Nepal’s Citizens’ Movement

This article considers the relationship of civil society to the domain of the political from the actors’ perspectives. It explores the attempt by a citizens’ movement (CMDP) in Nepal to construct new political realities in the context of the autocratic regime of king Gyanendra and then during the democratic transition. This was, paradoxically, to be achieved through the construction of an apolitical space. Theoretically, this production of apoliticality by civil society actors shows that civil society is not only implicated in the expansion of what is understood as ‘political’ but also in setting its boundaries. The broader aims of the article are to contribute to the ethnography of civil society and to add to current understandings of the relationship of actually existing civil societies to the political domain. Practically, it argues that debates over whether civil society is or is not political in the Nepal case and normative positions within development circles that it should not be political are misconceived since civil society is a site for the production of both politicality and apoliticality.     

An integrated lean and green approach for improving sustainability performance: a case study of a packaging manufacturing SME in the U.K.

Abstract

Competitive landscape, informed consumers and stringent regulations have forced many manufacturing small- and medium-sized enterprises (SMEs) to focus on operational efficiency along with sustainability issues in recent years. While many manufacturing organisations have been taking lean initiatives for the past few years for operational excellence, an impulsive rush to adopt lean without a strategic deployment vision has led to scattered implementation of lean tools and projects without desired success. Many researchers and practitioners prescribe value stream mapping as a foundation for lean transformation initiatives; however, little empirical work is available on the symbiosis of lean and green paradigms to reap maximum benefits. This research, through a systematic methodology and a novel tool called Green Integrated Value Stream Mapping (GIVSM), integrates both paradigms in a case study on a U.K. packaging-manufacturing SME. Applying the GIVSM demonstrates that simultaneous deployment of lean and green paradigms have synergistic effect for improving both operational efficiency and environmental performance. In addition, continuous improvement framework with sustainable procurement is proposed to overcome the lean-green misalignments. This study also provides a guiding reference for practitioners to undertake similar improvement projects and identifies opportunities to expand this academic research on integrated lean-green approach into other industry sectors.     

The dependence upon context of project critical success factors: test of the contingency hypothesis and effects of technological uncertainty and collectivism culture

Abstract

Although the relationship between critical success factors (CSFs) and project performance is established, evidence regarding the dependence on the context of CSFs is patchy. To advance this field, we conduct two complementary studies. Study 1 examines contingency theory regarding managerial CSFs using survey responses (N?=?211) of project management professionals from the United Kingdom. Using survey data from projects (N?=?336) in the United Kingdom, Study 2 examines the contextual dependence of managerial CSFs in a moderated-moderation, theoretical framework whereby project technological uncertainty moderates the relationship between managerial CSFs and project execution and efficiency, and in-group collectivism culture of the executing organisation moderates the effect of technological uncertainty. Results confirm that external and internal contexts influence managerial CSFs. Managerial CSFs have a greater than expected influence on project execution and efficiency. The positive effect of managerial CSFs is weaker when technological uncertainty is high. When technological uncertainty is high, the effect of managerial CSFs strengthens as levels of in-group collectivism culture increase. However, when technological uncertainty is low, the effect of managerial CSFs weakens as levels of in-group collectivism culture increase. We discuss the managerial and theoretical implications.     

Reliability Studies of the Log-Exponential Inverse Gaussian Distribution

In this article, we investigate the monotonicity of the density, failure rate, and mean residual life functions of the log-exponential inverse Gaussian distribution. It turns out that, in this case, the monotonicity of the density, failure rate, and mean residual life functions take different forms depending on the range of the parameters. Maximum likelihood estimators of the critical points of the density, failure rate, and mean residual life functions of the model are evaluated using Monte Carlo simulations. An example of a published data set is used to illustrate the estimation of the critical points.