The generalized likelihood ratio test for the Behrens-Fisher problem

A solution is suggested for the Behrens-Fisher problem of testing the equality of the means from two normal populations where variances are unknown and not assumed equal, by considering an adaption of the generalized likelihood ratio test. The test developed and called the adjusted likelihood ratio test has size close to the nominal significance level and compares favourably with regard to size and power to the Welch-Aspin test. An asymptotic result shows the connection between the generalized likelihood ratio test and the most commonly used test statistic for the Behrens-Fisher problem.     

Optimising the queuing system for an ear,nose and throat outpatient clinic

Several authors have considered the problem of the efficient running of hospital outpatient clinics. The first solution was probably by Welch & Bailey (1952). More recent authors include Fetter & Thompson (1966), Vissers (1979), Stafford & Aggarwal (1979). The Ear, Nose and Throat outpatient clinic presents a special case due to the complex queuing structure involved, which is described in the next section. A simulation of this special clinic was undertaken, any useful theoretical results being impossible to obtain.     

Semiparametric Modeling of the Spatial Distribution of Occupational Accident Risk in the Casual Labor Market, Piracicaba, Southeast Brazil

The objective of this study was to estimate the spatial distribution of work accident risk in the informal work market in the urban zone of an industrialized city in southeast Brazil and to examine concomitant effects of age, gender, and type of occupation after controlling for spatial risk variation. The basic methodology adopted was that of a population-based case-control study with particular interest focused on the spatial location of work. Cases were all casual workers in the city suffering work accidents during a one-year period; controls were selected from the source population of casual laborers by systematic random sampling of urban homes. The spatial distribution of work accidents was estimated via a semiparametric generalized additive model with a nonparametric bidimensional spline of the geographical coordinates of cases and controls as the nonlinear spatial component, and including age, gender, and occupation as linear predictive variables in the parametric component. We analyzed 1,918 cases and 2,245 controls between 1/11/2003 and 31/10/2004 in Piracicaba, Brazil. Areas of significantly high and low accident risk were identified in relation to mean risk in the study region (p < 0.01). Work accident risk for informal workers varied significantly in the study area. Significant age, gender, and occupational group effects on accident risk were identified after correcting for this spatial variation. A good understanding of high-risk groups and high-risk regions underpins the formulation of hypotheses concerning accident causality and the development of effective public accident prevention policies.     

MCMC implementation for Bayesian hidden semi-Markov models with illustrative applications

Hidden Markov models (HMMs) are flexible, well-established models useful in a diverse range of applications. However, one potential limitation of such models lies in their inability to explicitly structure the holding times of each hidden state. Hidden semi-Markov models (HSMMs) are more useful in the latter respect as they incorporate additional temporal structure by explicit modelling of the holding times. However, HSMMs have generally received less attention in the literature, mainly due to their intensive computational requirements. Here a Bayesian implementation of HSMMs is presented. Recursive algorithms are proposed in conjunction with Metropolis-Hastings in such a way as to avoid sampling from the distribution of the hidden state sequence in the MCMC sampler. This provides a computationally tractable estimation framework for HSMMs avoiding the limitations associated with the conventional EM algorithm regarding model flexibility. Performance of the proposed implementation is demonstrated through simulation experiments as well as an illustrative application relating to recurrent failures in a network of underground water pipes where random effects are also included into the HSMM to allow for pipe heterogeneity.     

The anatomy of a deception: Fraud and finesse in the Mock Auction sales ‘con’

In this paper we analyze recordings of the Mock Auction sales con and describe the various rhetorical and performative strategies employed by the seller/deceiver to accomplish sales success. Two features that distinguish this con from others are that sales are obtained from a crowd of shoppers and that the victims rarely complain after they have been deceived. We outline the principal skills that are brought into play by these salespeople to obtain sales and to manage the audiences' quietude. We show that the Mock Auction is, fundamentally, a social and interactional accomplishment.     

Corporate planning in South African companies

This paper is based on the research understaken by the author for his dostorate thesis. It describes the research methodology, data analysis and results of a survey of strategic planning as practised by South African companies, based over 500 questionnaires. The influence of the various interest groups revealed in the analysis is compared and discussed.     

NEIGHBORHOOD FAMILY-FRIENDLINESS AND ITS EFFECT ON FAMILY RELATIONS: EVIDENCE FROM UTAH

This article explores the effect of neighborhood family-friendliness on three measures of family relations: marital burnout, marital satisfaction, and parent-child relations. Regression analyses of survey data from northern Utah provide some support that neighborhood family-friendliness, measured here as neighborhood cohesion and neighborhood assessment, positively affects family functioning. For men, neighborhood cohesion was negatively associated with marital burnout and positively associated with marital satisfaction. For both men and women, neighborhood assessment was positively associated with marital satisfaction. These relationships were stronger for men than for women.