Density regression using repulsive distributions

Flexible regression is a traditional motivation for the development of non-parametric Bayesian models. A popular approach for this involves a joint model for responses and covariates, from which the desired result arises by conditioning on the covariates. Many such models involve the convolution of a continuous kernel with some discrete random probability measure defined as an infinite mixture of i.i.d. atoms. Following this strategy, we propose a flexible model that involves the concept of repulsion between atoms. We show that this results in a more parsimonious representation of the regression than the i.i.d. counterpart. The key aspect is that repulsion discourages mixture components that are near each other, thus favouring parsimony. We show that the conditional model retains the repulsive features, thus facilitating interpretation of the resulting flexible regression, and with little or no sacrifice of model fit compared to the infinite mixture case. We show the utility of the methodology by way of a small simulation study and an application to a well-known data set.     

Graphical comparison of normality tests for unimodal distribution data

A methodology is proposed to compare the power of normality tests with a wide variety of alternative unimodal distributions. It is based on the representation of a distribution mosaic in which kurtosis varies vertically and skewness horizontally. The mosaic includes distributions such as exponential, Laplace or uniform, with normal occupying the centre. Simulation is used to determine the probability of a sample from each distribution in the mosaic being accepted as normal. We demonstrate our proposal by applying it to the analysis and comparison of some of the most well-known tests.     

On the integrated maximum likelihood estimators for a closed population capture–recapture model with unequal capture probabilities

Nuisance parameter elimination is a central problem in capture–recapture modelling. In this paper, we consider a closed population capture–recapture model which assumes the capture probabilities varies only with the sampling occasions. In this model, the capture probabilities are regarded as nuisance parameters and the unknown number of individuals is the parameter of interest. In order to eliminate the nuisance parameters, the likelihood function is integrated with respect to a weight function (uniform and Jeffrey's) of the nuisance parameters resulting in an integrated likelihood function depending only on the population size. For these integrated likelihood functions, analytical expressions for the maximum likelihood estimates are obtained and it is proved that they are always finite and unique. Variance estimates of the proposed estimators are obtained via a parametric bootstrap resampling procedure. The proposed methods are illustrated on a real data set and their frequentist properties are assessed by means of a simulation study.     

The coefficient of variation asymptotic distribution in the case of non-iid random variables

Due to the widespread use of the coefficient of variation in empirical finance, we derive its asymptotic sampling distribution in the case of non-iid random variables to deal with autocorrelation and/or conditional heteroskedasticity stylized facts of financial returns. We also propose statistical tests for the comparison of two coefficients of variation based on asymptotic normality and studentized time-series bootstrap. In an illustrative example, we analyze the monthly return volatility of six stock market indexes during the years 1990–2007.     

The Lamé class of Lorenz curves

In this paper, the class of Lamé Lorenz curves is studied. This family has the advantage of modeling inequality with a single parameter. The family has a double motivation: it can be obtained from an economic model and from simple transformations of classical Lorenz curves. The underlying cumulative distribution functions have a simple closed form, and correspond to the Singh–Maddala and Dagum distributions, which are well known in the economic literature. The Lorenz order is studied and several inequality and polarization measures are obtained, including Gini, Donaldson–Weymark–Kakwani, Pietra, and Wolfson indices. Some extensions of the Lamé family are obtained. Fitting and estimation methods under two different data configurations are proposed. Empirical applications with real data are given. Finally, some relationships with other curves are included.     

The corrected VIF (CVIF)

In this paper, we propose a new corrected variance inflation factor (VIF) measure to evaluate the impact of the correlation among the explanatory variables in the variance of the ordinary least squares estimators. We show that the real impact on variance can be overestimated by the traditional VIF when the explanatory variables contain no redundant information about the dependent variable and a corrected version of this multicollinearity indicator becomes necessary.     

Perceptions of Stigmatization and Satisfaction with Services Received,Among Users of Social Welfare Services for the Child and the Family in 3 European Regions

A system of psychosocial indicators, based on atheoretical model describing stigma perceptions byusers and practitioners of social welfare services forchildren and their families, was tested in 3 Europeanregions: Catalonia (Spain), Wales and the Netherlands.Data collection from users included questions on theirsatisfaction with the professional providing theservice and on their involvement in decisions abouthim/her and his/her family. In the Catalan sample oneadditional item asked about satisfaction with theoverall support received.Multiple correspondence analysis showed a consistentpattern of answers for our construct stigmaperceptions, using our indicators system.Discriminant analysis showed that our model works withattributions as expected in 86,32% of cases.Surprisingly, in the discriminant analysis all thesatisfaction indicators were excluded by the stepwisemethod, showing no strong relation between stigmaperception related to a service, and satisfactionusing such a service.Such results suggest that service users clearlydiscriminate between the fact that a service isfunctioning in a stigmatizing way, and the fact theyare satisfied or not with the practitioner helpingthem, with services involving them in decisions, orwith the overall support received from welfareservices.     

THE INFORMATIZATION OF THE WORLDVIEW

The development of information and communication technology in the second half of the twentieth century in crucial respects resembles the development of mechanics in the sixteenth and seventeenth century as it has been described by Dijksterhuis in his study The Mechanization of the World Picture (first published in 1950). In both cases specific technological developments not only lead to important changes in the natural and human sciences, but also profoundly affect culture as a whole and eventually result in a fundamental change in worldview. In this article the author attempts to elucidate the present informatization of the worldview in a twofold way. First, against the background of Dijksterhuis' analysis of the concept of mechane, a clarification is given of the concept of information, which has become central to many sciences in the last decades. It is argued that much of the confusion and misuse that surrounds the application of this concept can be reduced by making a careful distinction between the pragmatic, semantic and syntactic dimensions of information. Second, on basis of this clarification, the author discusses the transformation from a mechanistic to an informationistic worldview. While the mechanistic worldview is characterized by the postulates of analysability, lawfulness and controllability, the informationistic worldview is characterized by the postulates of synthetizability, programmability and manipulability. It is argued that although the informationistic worldview in some respects (for instance in its mathematical orientation) is clearly a continuation of the mechanistic worldview, in other respects it fundamentally alters human experience and the evaluation of, and association with, reality.     

The Influence of Temporary Employment on Unemployment Exits in a Competing Risks Framework

Using Spanish longitudinal data from the period 1992–2004, this paper examines labour market transitions of the newly unemployed in order to investigate the determinants of unemployment duration in a competing risks framework with four destination states: temporary employment, permanent employment, self-employment and inactivity. Special emphasis is placed on the influence of previous job variables. We find that individuals who become unemployed due to the end of a temporary contract are more likely to exit unemployment by finding another temporary job and less likely to exit through permanent jobs, self-employment or inactivity. However, long tenures in temporary jobs enhance the probability of finding a permanent employment. Moreover, the length of the previous job, when it terminates due to a layoff, hinders the probability of moving to employment (either permanent or temporary).