BAYES EMPIRICAL BAYES APPROACH TO ESTIMATION OF THE FAILURE RATE IN EXPONENTIAL DISTRIBUTION

ABSTRACT

In the empirical Bayes (EB) decision problem consisting of squared error estimation of the failure rate in exponential distribution, a prior Λ is placed on the gamma family of prior distributions to produce Bayes EB estimators which are admissible. A subclass of such estimators is shown to be asymptotically optimal (a.o.). The results of a Monte Carlo study are presented to demonstrate the a.o. property of the Bayes EB estimators.     

A bayesian analysis of trend determination in economic time series

In this paper we provide a comprehensive Bayesian posterior analysis of trend determination in general autoregressive models. Multiple lag autoregressive models with fitted drifts and time trends as well as models that allow for certain types of structural change in the deterministic components are considered. We utilize a modified information matrix-based prior that accommodates stochastic nonstationarity, takes into account the interactions between long-run and short-run dynamics and controls the degree of stochastic nonstationarity permitted. We derive analytic posterior densities for all of the trend determining parameters via the Laplace approximation to multivariate integrals. We also address the sampling properties of our posteriors under alternative data generating processes by simulation methods. We apply our Bayesian techniques to the Nelson-Plosser macroeconomic data and various stock price and dividend data. Contrary to DeJong and Whiteman (1989a,b,c), we do not find that the data overwhelmingly favor the existence of deterministic trends over stochastic trends. In addition, we find evidence supporting Perron's (1989) view that some of the Nelson and Plosser data are best construed as trend stationary with a change in the trend function occurring at 1929.     

Amemiya‘s generalized least squares and tests of overidentification in simultaneous equation models with qualitative or limited dependent variables

Amemiya's generalized least squares method for the estimation of simultaneous equation modeis with qualitative or limited dependent variables is known to be efficient relative to many popular two stage estimators. This note points out that test statistics for overidentification restrictions can be obtained as by-products of Amerniya's generalized least squares procedure. Amemiya's procedure is shown to be a minimum chisquare method. The Amemiya procedure is valuable both for efficient estimation and for model evaluation of such models.     

Analysis of accelerated life tests with weibull failure distribution via generalized linear models

Efficient industrial experiments for reliability analysis of manufactured goods may consist in subjecting the units to higher stress levels than those of the usual working conditions. This results in the so called "accelerated life tests" where, for each pre-fixed stress level, the experiment ends after the failure of a certain pre-fixed proportion of units or a certain test time is reached. The aim of this paper is to determine estimates of the mean lifetime of the units under usual working conditions from censored failure data obtained under stress conditions. This problem is approached through generalized linear modelling and related inferential techniques, considering a Weibull failure distribution and a log-linear stress-response relationship. The general framework considered has as particular cases, the Inverse Power Law model, the Eyring model, the Arrhenius model and the generalized Eyring model. In order to illustrate the proposed methodology, a numerical example is provided.     

Understanding the dynamic interinfluences of implementation processes: An illustration by multiple case studies

Many dropout prevention programs have been developed and validated in the past decades. Yet, little is known about the contextual factors influencing the implementation of these programs. Implementation processes, such as school principal leadership and governmental funding, have been identified for their influence on program implementation, but the mutual or dynamic influence of these processes is yet to be understood. This study examines the processes involved in the implementation of Check & Connect (C&C), a well-established targeted dropout prevention program validated in several countries that aims at promoting the development of a significant relationship between at-risk students and a mentor as a way to prevent school dropout.Semi-structured interviews were conducted with 12 mentors and coordinators directly involved in C&C implementation. Analyses were conducted in two subsequent steps: thematic analyses first helped identify implementation processes described by respondents, and then synthetic case studies allowed us to build the implementation stories of distinct sites. This last step was conducted using the Planned Change Framework.This framework helped us to understand the complex dynamics of implementation processes in each site, which were associated with previously identified program outcomes, beyond implementation fidelity. Implications for future implementations of evidence-based programs in the school setting are discussed.     

Strengthening implementation success using large-scale consensus decision-making - A new approach to creating medical practice guidelines

A study involving over 2000 stoma care nurses in the development of best practice guidelines for the assessment of peristomal body profiles, patient engagement and patient follow-up was conducted in 2018. The study was designed to develop guidelines for stoma care treatment and product selection and to decrease the evidence to implementation gap. The project built on research evidence from a literature review of 77 articles. The results of the literature review were then used to inform a series of Delphi surveys sent out to stoma care nurses through Association and industry list-serves in 11 languages. The Delphi surveys were followed by a face2face professionally facilitated discussions among nurse-research experts. The project concluded with a facilitated consensus dialogue among 960 stoma care nurses from 25 countries, resulting in an implementation plan to ensure the guidelines become a normal part of routine patient care. The study resulted in a set of medical practice guidelines for stoma care nurses, designed to improve patient outcomes and patient quality of life, that were accepted and adopted into routine medical practice across 25 countries. This article describes the study and how the process used, coined the ‘Modified Delphi Process’ by the process designer, led to faster implementation than is generally experienced in the medical community.     

Development and validation of an instrument to assess institutionalization of health promotion in faith-based organizations

Institutionalization of health promotion interventions occurs when the organization makes changes to support the program as a component of its routine operations. To date there has not been a way to systematically measure institutionalization of health promotion interventions outside of healthcare settings. The purpose of the present study was to develop and evaluate the initial psychometric properties of an instrument to assess institutionalization (i.e., integration) of health activities into faith-based organizations (i.e., churches). This process was informed by previous institutionalization models led by a team of experts and a community-based advisory panel. We recruited African American church leaders (N = 91) to complete a 22-item instrument. An exploratory factor analysis revealed four factors: 1) Organizational Structures (e.g., existing health ministry, health team), 2) Organizational Processes (e.g., records on health activities; instituted health policy), 3) Organizational Resources (e.g., health promotion budget; space for health activities), and 4) Organizational Communication (e.g., health content in church bulletins, discussion of health within sermons) that explained 62.3 % of the variance. The measure, the Faith-Based Organization Health Integration Inventory (FBO-HII), had excellent internal consistency reliability (α = .89) including the subscales (α = .90, .82, .81, and .87). This measure has promising initial psychometric properties for assessing institutionalization of health promotion interventions in faith-based settings.     

A Mathematical Model of Service Failure and Recovery Strategies*

Understanding the nature of service failures and their impact on customer responses and designing cost‐effective recovery strategies have been recognized as important issues by both service researchers and practitioners. We first propose a conceptual framework of service failure and recovery strategies. We then transform it into a mathematical model to assist managers in deciding on appropriate resource allocations for outcome and process recovery strategies based on customer risk profiles and the firm's cost structures. Based on this mathematical model we derive optimal recovery strategies, conduct sensitivity analyses of the optimal solutions for different model parameters, and illustrate them through numerical examples. We conclude with a discussion of managerial implications and directions for future research.     

An Exploratory Analysis of the Value of the Skills of IT Personnel: Their Relationship to IS Infrastructure and Competitive Advantage

Determining and assessing the requisite skills of information technology (IT) personnel have become critical as the value of IT has risen in modern organizations. In addition to technical skills traditionally expected of IT personnel, softer skills like managerial, business, and interpersonal skills have been increasingly cited in previous studies as mandatory for these employees. This paper uses a typology of IT personnel skills—technology management skills, business functional skills, interpersonal skills, and technical skills—and investigates their relationships to two information systems (IS) success variables, IS infrastructure flexibility and the competitive advantage provided by IS. The study investigates these relationships using the perceptions of chief information officers (CIOs) from mostly Fortune 2000 companies. The contributions of this study are: IT personnel skills do affect IS success, technical skills are viewed as the most important skill set in affecting IS infrastructure flexibility and competitive advantage, and modularity is viewed as more valuable to competitive advantage than integration. Several explanations are offered for the lack of positive relationships between the softer IT personnel skills and the dimensions of IS success used in this study.