Maximum Likelihood Unit Root Testing in the Presence of GARCH: A New Test with Increased Power

The literature on testing the unit root hypothesis in the presence of GARCH errors is extended. A new test based upon the combination of local-to-unity detrending and joint maximum likelihood estimation of the autoregressive parameter and GARCH process is presented. The finite sample distribution of the test is derived under alternative decisions regarding the deterministic terms employed. Using Monte Carlo simulation, the newly proposed ML t-test is shown to exhibit increased power of relative to rival tests. Finally, the empirical relevance of the simulation results is illustrated via an application to real GDP for the UK.     

Bayesian Network for Risk of Diarrhea Associated with the Use of Recycled Water

Estimating potential health risks associated with recycled (reused) water is highly complex given the multiple factors affecting water quality. We take a conceptual model, which represents the factors and pathways by which recycled water may pose a risk of contracting gastroenteritis, convert the conceptual model to a Bayesian net, and quantify the model using one expert's opinion. This allows us to make various predictions as to the risks posed under various scenarios. Bayesian nets provide an additional way of modeling the determinants of recycled water quality and elucidating their relative influence on a given disease outcome. The important contribution to Bayesian net methodology is that all model predictions, whether risk or relative risk estimates, are expressed as credible intervals.     

Robust inference for bivariate point processes

In the analysis of recurrent events where the primary interest lies in studying covariate effects on the expected number of events occurring over a period of time, it is appealing to base models on the cumulative mean function (CMF) of the processes (Lawless & Nadeau 1995). In many chronic diseases, however, more than one type of event is manifested. Here we develop a robust inference procedure for joint regression models for the CMFs arising from a bivariate point process. Consistent parameter estimates with robust variance estimates are obtained via unbiased estimating functions for the CMFs. In most situations, the covariance structure of the bivariate point processes is difficult to specify correctly, but when it is known, an optimal estimating function for the CMFs can be obtained. As a convenient model for more general settings, we suggest the use of the estimating functions arising from bivariate mixed Poisson processes. Simulation studies demonstrate that the estimators based on this working model are practically unbiased with robust variance estimates. Furthermore, hypothesis tests may be based on the generalized Wald or generalized score tests. Data from a trial of patients with bronchial asthma are analyzed to illustrate the estimation and inference procedures.     

Peers influence the tobacco and alcohol use of Chinese adolescents

This two-wave longitudinal study examined peer selection and influence pertaining to tobacco and alcohol use by adolescents and their friends in a sample of 854 Chinese adolescents (384 girls: mean age = 13.33 years). Participants nominated friends and self-reported their tobacco and alcohol use at seventh and again at eighth grade. Longitudinal social network analyses revealed evidence of friend influence but not selection over smoking and drinking. Boys increased their levels of smoking at rates greater than that of girls, but no sex moderation of either selection or influence was found. In interpreting these results, it is important to understand the gender norms for Chinese boys and girls and the cultural context of tobacco and alcohol use.     

Jography: Exploring Meanings,Experiences and Spatialities of Recreational Road-running

Jogging is a relatively under-researched mobile practice with much existing literature focusing on ‘serious’ and competitive running. In this paper, we provide an account of some of the movements, meanings and experiences that together help produce the practice of jogging in the south-western English city of Plymouth. Drawing upon participant diaries and interviews, we uncover rich detail about how joggers ascribe not one but a number of meanings to their practice. Some of these are positive, some are negative; some complement each other and some compete with each other. We also consider how the experiences of joggers can be shaped by their ongoing need to develop tactics capable of enabling them to negotiate space with non-joggers. This is in some contrast to more competitive running that occurs in the separated space of an athletics track. Our sense is that better awareness of the meanings and experiences of jogging will be of value if the advertised health and sustainability benefits of the practice are to be more effectively encouraged and promoted.     

The incidence of anabolic steroid use among competitive bodybuilders

The purpose of this study was to determine the incidence of anabolic steroid use among competitive male and female bodybuilders in Kansas and Missouri. A profile was established for users and non-users of anabolic steroids. The results of this study indicated that more than half of the male bodybuilders (54%) were using steroids on a regular basis compared to 10 percent of the female competitors. The types of steroid used were investigated and revealed that on average, four different types of anabolic steroid were used during the year, with individual use ranging from one to fifteen different types; including Dianabol, Deca Durabolin, Anavar, Testosterone, Androl 50, Winstrol, Primobolan, Equipoise, Finaject, Parabolin, HCG, Primacetate, Enanthate, Halotestin, and Maxibolin, in order of the most to least frequently used. The female bodybuilders reported that they had used an average of two different steroids including Deca Durabolin, Anavar, Testosterone, Dianabol, Equipoise, and Winstrol. The principal reason bodybuilders used steroids was related to their perception that these drugs were an important factor in winning competitions. Another important motivating factor for use was consistent with reports that significant gains in strength could be achieved by including anabolic steroids as part of the training regimen in spite of the reported adverse side-effects.     

The relation of economic factors to perceived stress in mobile families

The purpose of this research is to examine the relationship between objective and subjective measures of economic well-being, amount of and satisfaction with control, and perceived stress level of subjects, who have relocated with their families within the past year. Both males and females indicate more stress if their financial condition is worse following the move than before, if their employment status is not satisfying, and when they have little control over their lives and are not satisfied with their level of control. Stress is negatively related to satisfaction with the specific aspects of economic situation studied for both males and females with limited exception.Peggy S. Berger received her Ph.D. from Pennsylvania State University. She is an Associate Professor in the Department of Consumer Sciences, Colorado State University, Fort Collins, CO 80523. Her research interests include socioeconomic issues related to geographic mobility and to gender, and work and family issues.Judith Powell received her Ph.D. from Oklahoma State University. She is a Professor of Child and Family Studies, and Head of the Department of Home Economics, University of Wyoming, Laramie, WY 82071. Her research interests include parent-child relations and effects of relocation on families.Alicia Skinner Cook received her Ph.D. from Arizona State University. She is a Professor in the Department of Human Development and Family Studies at Colorado State University, Fort Collins, CO 80523. Her research interests include grief and loss issues, family stress, and adjustment to relocation.     

A theory of organizational response to hospital regulation: a reply to Smith and Mick

Smith and Mick identify four basic problems with the theory the present writers developed to explain organizational responses (in this case the behavior of hospitals) to regulation. They challenge the basic assumption regarding autonomy, disagree with the implied cause and effect relations between organizational response and regulation, criticize the omission of goals, and claim that the theory has only limited generality. In so doing they state that their primary concern is with "improving our understanding of the limitations and benefits of the theory." Each of the four topics they raise for consideration will receive comment.