Bootstrapping in least absolute value regression: an application to hypothesis testing

A Monte Carlo simulation is used to study the performance of hypothesis tests for regression coefficients when least absolute value regression methods are used. In small samples, the results of the simulation suggest that using the bootstrap method to compute standard errors will provide improved test performance     

More Powerful Tests from Confidence Interval p Values

In this article the problem of comparing two independent binomial populations is considered. It is shown that the test based on the confidence interval p value of Berger and Boos often is uniformly more powerful than the standard unconditional test. This test also requires less computational time.     

Correlation,Regression Lines,and Moments of Inertia

The R language, a freely available environment for statistical computing and graphics is widely used in many fields. This “expert-friendly” system has a powerful command language and programming environment, combined with an active user community. We discuss how R is ideal as a platform to support experimentation in mathematical statistics, both at the undergraduate and graduate levels. Using a series of case studies and activities, we describe how R can be used in a mathematical statistics course as a toolbox for experimentation. Examples include the calculation of a running average, maximization of a nonlinear function, resampling of a statistic, simple Bayesian modeling, sampling from multivariate normal, and estimation of power. These activities, often requiring only a few dozen lines of code, offer students the opportunity to explore statistical concepts and experiment. In addition, they provide an introduction to the framework and idioms available in this rich environment.     

Returning to YTS: the long-term impact of youth training scheme participation

ABSTRACT

Shortly after leaving Leicester for Scotland Andy Furlong began to wrestle with the complexities of school to work transitions as captured by the 1986 sweep of the British Cohort Study (BCS). His analysis was published as Schooling for Jobs. Although a relatively short text, this book was vitally important as it documented in detail, for the first time, the changes to career preparations of British secondary school children at the mid-point of a decade where the impact of deindustrialising processes, coupled with the neo-liberal policies of the political right, had ravaged the UK economy and decimated the youth labour market. The mid 1980s were a turning point that marked a shift to ‘individuals’ having responsibility for future career successes and the blaming of young people themselves for any perceived labour market failings. Central to this process was the Youth Training Scheme (YTS). Based on recent collaborations with Andy exploring YTS we have two main aims here. First, we revisit the BCS data to update the story and answer three interrelated questions: (i) what happened to the YTS participants from Furlong’s analysis?; (ii) what were the long-term career and life ‘impacts’ for those who participated in YTS during the 1980s?; and (iii) were these job substitution schemes or gateways to real and meaningful work? Second, we conclude by reflecting upon this aspect of Andy’s legacy and the shape of future research on youth training schemes.     

Indicator development as a site of collective imagination? The case of European Commission policies on the circular economy

ABSTRACT

In recent years the concept of the circular economy gained prominence in EU policy-making. The circular economy promotes a future in which linear ‘make-use-dispose’ cultures are replaced by more circular models. In this paper, we use the concept of sociotechnical imaginaries to ask how an imaginary of circularity has been assembled and stabilized, which imaginative resources were drawn on, and how goals, priorities, benefits and risks haven been merged with discourses of innovation, sustainability and growth. Drawing on policy documents and interviews with policy officers of the European Commission, we argue that the monitoring framework and indicator development function as a site collective imagination in which desirable ‘circular’ futures are co-produced. These futures are imagined to provide novel opportunities for the private sector and to generate jobs and economic growth while at the same time improving the natural environment as measured by selected environmental indicators.     

Evolution of Quality: First Fifty Issues of Production and Operations Management

Many contributions have been made to the field of quality since the inaugural issue of Production and Operations Management in 1992. The first issue called for more research and teaching on TQM, which resulted in two special issues dedicated to TQM. Many other articles related to quality have also been published in the first fifty issues of the journal on topics ranging from technical methods to the Baldrige Award and ISO 9000. As we review these articles, we assess their contribution and the progression of the field of quality. Although past research has advanced our understanding of quality, there still exists many research opportunities in developing more theory, using additional research methodologies, and studying emerging topics in this field.     

An Analytical Investigation of the Bullwhip Effect

The Bullwhip Effect is problematic: order variability increases as orders propagate along the supply chain. The fundamental differential delay equations for a retailer's inventory reacting to a surge in demand are solved exactly. Much of the rich and complex inventory behavior is determined by the replenishment delay. The analytical solutions agree with numerical integrations and previous control theory results. Managerially useful ordering strategies are proposed. Exact expressions are derived for the retailer's orders to the manufacturer, and the Bullwhip Effect arises naturally. The approach is quite general and applicable to a wide variety of supply chain problems.     

THE ROLE OF MARITAL STATUS IN HEALTH SERVICES EXPENDITURES FOR PSYCHIATRIC OUTPATTIENTS

This study tested the hypothesis that married psychiatric outpatients would have lower total health services expenditures than divorced or separated patients. Chart review of the 471 individuals attending an academic medical center outpatient psychiatric clinic during 1994 identified 131 married, 40 separated, and 93 divorced patients. Separated men had significantly higher average total charges ($16,890) than married ($5,279) or divorced ($5,539) men by one-way ANOVA (p < .05). The nonparametric Mann-Whitney test also showed that separated men had higher charges than married or divorced men. There were no differences between marital status groups for women.     

Distribution of Exposure Concentrations and Doses for Constituents of Environmental Tobacco Smoke

The ultimate goal of the research reported in this series of three articles is to derive distributions of doses of selected environmental tobacco smoke (ETS)-related chemicals for nonsmoking workers. This analysis uses data from the 16-City Study collected with personal monitors over the course of one workday in workplaces where smoking occurred. In this article, we describe distributions of ETS chemical concentrations and the characteristics of those distributions (e.g., whether the distribution was log normal for a given constituent) for the workplace exposure. Next, we present population parameters relevant for estimating dose distributions and the methods used for estimating those dose distributions. Finally, we derive distributions of doses of selected ETS-related constituents obtained in the workplace for people in smoking work environments. Estimating dose distributions provided information beyond the usual point estimate of dose and showed that the preponderance of individuals exposed to ETS in the workplace were exposed at the low end of the dose distribution curve. The results of this analysis include estimations of hourly maxima and time-weighted average (TWA) doses of nicotine from workplace exposures to ETS (extrapolated from 1 day to 1 week) and doses derived from modeled lung burdens of ultraviolet-absorbing particulate matter (UVPM) and solanesol resulting from workplace exposures to ETS (extrapolated from 1 day to 1 year).