Weighted Logrank Permutation Tests for Randomly Right Censored Life Science Data

In biomedical research, weighted logrank tests are frequently applied to compare two samples of randomly right censored survival times. We address the question how to combine a number of weighted logrank statistics to achieve good power of the corresponding survival test for a whole linear space or cone of alternatives, which are given by hazard rates. This leads to a new class of semiparametric projection tests that are motivated by likelihood ratio tests for an asymptotic model. We show that these tests can be carried out as permutation tests and discuss their asymptotic properties. A simulation study together with the analysis of a classical data set illustrates the advantages.     

Bayesian Analysis of Instrumental Variable Models: Acceptance-Rejection within Direct Monte Carlo

We discuss Bayesian inferential procedures within the family of instrumental variables regression models and focus on two issues: existence conditions for posterior moments of the parameters of interest under a flat prior and the potential of Direct Monte Carlo (DMC) approaches for efficient evaluation of such possibly highly non-elliptical posteriors. We show that, for the general case of m endogenous variables under a flat prior, posterior moments of order r exist for the coefficients reflecting the endogenous regressors’ effect on the dependent variable, if the number of instruments is greater than m +r, even though there is an issue of local non-identification that causes non-elliptical shapes of the posterior. This stresses the need for efficient Monte Carlo integration methods. We introduce an extension of DMC that incorporates an acceptance-rejection sampling step within DMC. This Acceptance-Rejection within Direct Monte Carlo (ARDMC) method has the attractive property that the generated random drawings are independent, which greatly helps the fast convergence of simulation results, and which facilitates the evaluation of the numerical accuracy. The speed of ARDMC can be easily further improved by making use of parallelized computation using multiple core machines or computer clusters. We note that ARDMC is an analogue to the well-known “Metropolis-Hastings within Gibbs” sampling in the sense that one ‘more difficult’ step is used within an ‘easier’ simulation method. We compare the ARDMC approach with the Gibbs sampler using simulated data and two empirical data sets, involving the settler mortality instrument of Acemoglu et al. (2001 Acemoglu , D. , Johnson , S. , Robinson , J. A. ( 2001 ). The colonial origins of comparative development: An empirical investigation . American Economic Review 91 ( 5 ): 1369 – 1401 .[Crossref], [Web of Science ®] , [Google Scholar]) and father's education's instrument used by Hoogerheide et al. (2012a Hoogerheide , L. F. , Block , J. H. , Thurik , A. R. (2012a). Family background variables as instruments for education in income regressions: A Bayesian analysis. Economics of Education Review 31(5):515–523.[Crossref], [Web of Science ®] , [Google Scholar]). Even without making use of parallelized computation, an efficiency gain is observed both under strong and weak instruments, where the gain can be enormous in the latter case.     

Simple components

Interpretation of principal components is difficult due to their weights (loadings, coefficients) being of various sizes. Whereas very small weights or very large weights can give clear indication of the importance of particular variables, weights that are neither large nor small (‘grey area’ weights) are problematical. This is a particular problem in the fast moving goods industries where a lot of multivariate panel data are collected on products. These panel data are subjected to univariate analyses and multivariate analyses where principal components (PCs) are key to the interpretation of the data. Several authors have suggested alternatives to PCs, seeking simplified components such as sparse PCs. Here components, termed simple components (SCs), are sought in conjunction with Thurstonian criteria that a component should have only a few variables highly weighted on it and each variable should be weighted heavily on just a few components. An algorithm is presented that finds SCs efficiently. Simple components are found for panel data consisting of the responses to a questionnaire on efficacy and other features of deodorants. It is shown that five SCs can explain an amount of variation within the data comparable to that explained by the PCs, but with easier interpretation.     

Do healthy diets in Europe matter to the environment? A quantitative analysis

Final consumption of food products figures amongst the strongest contributors to negative environmental impacts in Europe, with the production of beef and pork at agricultural level being the main responsible part of the food supply chain. This article analyses quantitatively the environmental impact of changing European diets. The environmental impact of European consumption is determined with an environmental extended input-output analysis, supplemented by a partial equilibrium model reflecting changes of the agricultural sector to modified diets. It results that agricultural production does not decrease significantly in reaction to reduced food consumption, due to a changed trade balance and substitution effects.     

“We build a better beagle”: Fantastic creatures in lab animal ads

The lab animal's significance and meaning are at the heart of the experimental method in modern biomedical research. Sociologists, however, have been remiss in studying how these animals are socially constructed within the scientific community as well as by industries, such as animal breeders, that support such research. Inspection of the advertisements used by breeding companies reveals three images of lab animals—the classy chemical, the consumer good, and the team player. The possible appeal of such images to readers of these ads is explored.     

Social Monitoring as Social Control: The Case of Drug Testing in a Medical Workplace

While workplace drug testing has received considerable public and scholarly attention, little of this discussion has focused on the social context within which testing is likely to occur. This paper conceptualizes drug testing as social monitoring and examines testing within a framework suggested by Donald Black's theory of social control. The central idea is that the formality of social monitoring within a group is a function of its members' social status and the social distance among them. The paper evaluates this argument in one empirical setting. Analysis of data from U.S. departments of anesthesiology indicates that drug testing, an example of formal monitoring, most often emerges in a context marked by low normative respectability and a lack of intimate relationships. The paper concludes by suggesting how variations in monitoring procedures like drug testing may affect ensuing processes of social control.     

Fuzzy prior information and minimax estimation in the linear regression model

We consider the linear regression modely=Xβ+u with prior information on the unknown parameter vector β. The additional information on β is given by a fuzzy set. Using the mean squared error criterion we derive linear estimators that optimally combine the data with the fuzzy prior information. Our approach generalizes the classical minimax procedure firstly proposed by Kuks and Olman.     

Suicidal behavior among members of Gamblers Anonymous

A national sample of 500 members of Gamblers Anonymous was surveyed by mail in order to gather information on suicidal history. One hundred sixty two usable surveys were returned representing 32.4% of the original sample. Compulsive gamblers who had a history of suicidal preoccupation began gambling at an earlier age than nonsuicidal gamblers and were more likely to have stolen to support their gambling. They also tended to have addicted relatives and children more than nonsuicidal gamblers did. The data suggest that those gamblers who had been suicidal tend to be more serious gamblers than nonsuicidal respondents.