Analysis of middle-censored data with exponential lifetime distributions

Recently Jammalamadaka and Mangalam [2003. Non-parametric estimation for middle censored data. J. Nonparametric Statist. 15, 253–265] introduced a general censoring scheme called the “middle-censoring” scheme in non-parametric set up. In this paper we consider this middle-censoring scheme when the lifetime distribution of the items is exponentially distributed and the censoring mechanism is independent and non-informative. In this set up, we derive the maximum likelihood estimator and study its consistency and asymptotic normality properties. We also derive the Bayes estimate of the exponential parameter under a gamma prior. Since a theoretical construction of the credible interval becomes quite difficult, we propose and implement Gibbs sampling technique to construct the credible intervals. Monte Carlo simulations are performed to evaluate the small sample behavior of the techniques proposed. A real data set is analyzed to illustrate the practical application of the proposed methods.     

A Dynamic Perspective on Diverse Teams: Moving from the Dual-Process Model to a Dynamic Coordination-based Model of Diverse Team Performance

The existing literature on diverse teams suggests that diversity is both helpful to teams in making more information available and encouraging creativity and damaging to teams in reducing cohesion and information sharing. Thus the extant literature suggests that diversity within teams is a double-edged sword that leads to both positive and negative effects simultaneously. This literature has not, however, fully embraced the increasing calls in the broader groups literature to take account of time in understanding how groups function [e.g. Cronin, M. A., Weingart, L. R., &; Todorova, G. (2011). Dynamics in groups: Are we there yet? The Academy of Management Annals, 5, 571–612]. We review the literature on diverse teams employing this lens to develop a dynamic perspective that takes account of the timing and flow of diversity's effects. Our review suggests that diversity in groups has different short-term and long-term effects in ways that are not fully captured by the currently dominant double-edged sword metaphor. We identify an emerging perspective that suggests a tropical depression metaphor—that has the potential, over time, to develop either into a dangerous hurricane or diffuse into a rainstorm that gives way to sunshine, as more apt to capture the dynamic effects of diversity in teams. We conclude by outlining an agenda for redirecting future research on diverse teams using this more dynamic perspective.     

Some nonparametric precedence-type tests based on progressively censored samples and evaluation of power

In this paper, we consider the problem of testing the equality of two distributions when both samples are progressively Type-II censored. We discuss the following two statistics: one based on the Wilcoxon-type rank-sum precedence test, and the second based on the Kaplan–Meier estimator of the cumulative distribution function. The exact null distributions of these test statistics are derived and are then used to generate critical values and the corresponding exact levels of significance for different combinations of sample sizes and progressive censoring schemes. We also discuss their non-null distributions under Lehmann alternatives. A power study of the proposed tests is carried out under Lehmann alternatives as well as under location-shift alternatives through Monte Carlo simulations. Through this power study, it is shown that the Wilcoxon-type rank-sum precedence test performs the best.     

Physiologically-Based Pharmacokinetic Modeling of a Mixture of Toluene and Xylene in Humans

A physiologically-based pharmacokinetic (PBPK) model for a mixture of toluene (TOL) and xylene (XYL), developed and validated in the rat, was used to predict the uptake and disposition kinetics of TOL/XYL mixture in humans. This was accomplished by substituting the rat physiological parameters and the blood:air partition coefficient with those of humans, scaling the maximal velocity for hepatic metabolism on the basis of body weight^0.75, and keeping all other model parameters species-invariant. The human TOL/XYL mixture PBPK model, developed based on the quantitative biochemical mechanism of interaction elucidated in the rat (i.e., competitive metabolic inhibition), simulated adequately the kinetics of TOL and XYL during combined exposures in humans. The simulations with this PBPK model indicate that an eight hour co-exposure to concentrations that remain within the current threshold limit values of TOL (50 ppm) and XYL (100 ppm) would not result in significant pharmacokinetic interferences, thus implying that data on biological monitoring of worker exposure to these solvents would be unaffected during co-exposures.     

Inventor knowledge recombination behaviors in a pharmaceutical merger: The role of intra-firm networks

We study firms' abilities to increase the generative appropriability of their knowledge by studying the knowledge recombination patterns of inventors in the context of a merger between two equally sized pharmaceutical firms. Specifically, we study inventors' choices to recombine knowledge originating in the firm with which they merge. We hypothesize that mergers focus inventors' attention to units of knowledge originating in the other firm and that therefore, inventors will choose to recombine more of this knowledge, which exists in their intra-firm network, following a merger. We also hypothesize that inventors vary in terms of their recombination choices following a merger. We explore these differences by linking inventors' network positions with their abilities and motivations to recombine knowledge originating in the other firm. Specifically, we hypothesize an inverted-U shaped relationship between centrality and knowledge recombination from the other firm and a linear relationship between brokerage and knowledge recombination from the other firm. We test our hypotheses using patent data from the merger between Bristol-Myers and Squibb and find support for our hypotheses. The paper contributes to knowledge recombination research by exploring changes in knowledge recombination dynamics following a merger and by understanding how mergers affect firms’ generative research trajectories. Practically, we suggest that managers should identify and nurture certain types of inventors following a merger to be able to better leverage the knowledge bases of merging firms.     

Prioritising indicators in improving supply chain performance using fuzzy AHP: insights from the case example of four Indian manufacturing companies

Abstract

In this contribution, we aim to prioritise the indicators to enhance the organisational supply chain’s (SC) effectiveness from an industrial perspective. It will help industries to develop strategies for managing the SC effectively and ensuring improvement in performance continuously. To achieve this, this work proposes to use a two-phase research methodology. First, 36 SC performance improvement indicators are recognised from a literature survey and from field and industrial expert’s inputs. Secondly, a structural model is proposed using the fuzzy analytical hierarchy process (AHP) to prioritise the indicators strategically to improve the SC performance. The fuzzy AHP method helps determine the priority of concerns of the identified indicators under fuzzy surroundings. Inputs in this research are taken from four ancillary Indian plastic manufacturing firms. Research findings indicate that collaborations and information exchange dimension indicators obtained the highest priority in improving SC performance. The model proposed is considered very useful for the SC managers/practitioners/decision-makers to understand better and distinguish the essential SC performance improvement indicators and to take systematic decisions specifically to improve the performance of business in a SC context. Sensitivity analysis was conducted to examine the priority ranking of the indicators.     

Developing human resource competencies: an empirical evidence

The paper conceptually defines and empirically investigates the density of work experience along with individual characteristics (cognitive ability, Conscientiousness, and Openness to Experience) and examine their influence on Human Resource (HR) competencies. 274 HR executives from diverse industry background and their supervisors participated in the data collection efforts spread over three phases. Data analyses revealed three key findings (i) executives’ density of work experience positively relates to HR competencies, (ii) executives’ cognitive ability is the strongest predictor of the positive relationship to HR competencies, and (iii) executives with high Conscientiousness tend to achieve levels of density of work experience. Relative weight analyses reinforce that cognitive ability and density of work experience are the most prominent predictors of HR competencies. Implications for practice are discussed.     

Composite sampling: effectiveness under a two stage scheme

This article describes a two stage composite sampling scheme for the detection of defectives in a sample. The costs under these schemes are compared with the costs under exhaustive testing for the binomial and hypergeometric models.