Choice of the ridge factor from the correlation matrix determinant

Ridge regression is the alternative method to ordinary least squares, which is mostly applied when a multiple linear regression model presents a worrying degree of collinearity. A relevant topic in ridge regression is the selection of the ridge parameter, and different proposals have been presented in the scientific literature. Since the ridge estimator is biased, its estimation is normally based on the calculation of the mean square error (MSE) without considering (to the best of our knowledge) whether the proposed value for the ridge parameter really mitigates the collinearity. With this goal and different simulations, this paper proposes to estimate the ridge parameter from the determinant of the matrix of correlation of the data, which verifies that the variance inflation factor (VIF) is lower than the traditionally established threshold. The possible relation between the VIF and the determinant of the matrix of correlation is also analysed. Finally, the contribution is illustrated with three real examples.     

Prohibition,Regulation or Free Market: A Mapping of Colombian People’s Perspectives Regarding National Drug Policies

Colombian laypersons’ perspectives regarding actual and potential drug policies were examined. Adults (N = 395) aged 18–68 and living in Bogota were presented with 24 vignettes that were composed according to two within-subject orthogonal factor designs: (a) Demand for drugs in the country × Current government policy regarding soft and hard drugs (from “laissez faire” policy for all drugs to complete prohibition of all drugs) and (b) Information campaigns regarding the dangerousness of drugs × Current policy. Participants rated the level of acceptability of each policy. Seven different perspectives were identified that can be grouped into five broad views. The first one (50 % of participants) was called “radical constructionists” because participants considered that all policies were unacceptable. The second one (19 %) was called “cultural conservatives” because only one drug policy was considered fully acceptable: complete prohibition (although half of the members of this group were willing to allow soft drugs to be sold freely). The third one (14 %) was called “progressive prohibitionists” because the preferred policies in this group were either complete prohibition or complete regulation by the government. The fourth one (8 %) was called “free trade libertarians” because the dominant opinion was that the drug market should be free. The last one (5 %) was called “progressive advocates of legalization” because the preferred policy in this group was complete regulation of all substances. In most cases, the presence of information campaigns was highly valued. Methodological implications and implications for decision-makers are discussed.     

Settlers,target-earners,young professionals. Distinct migrant types,distinct integration trajectories?

In this article, we start out from theoretical concepts about different types of migrants that feature prominently in the immigration literature. By applying latent class analysis to a unique ‘mini-panel’ data set on recent Polish and Turkish immigrants in Germany, we identify two types of migrants that are in line with the literature, namely settlers and target-earners. We label a third group that is best described as educational target-earners: ‘young learners/professionals’. Regarding variation in these groups’ early sociocultural integration patterns, results suggest that they reflect primarily differences in migrants’ intention to stay, individual resources such as education, and opportunities for integration related to newcomers’ involvement in the educational system or labour force. In sum, migrant types – though certainly more intuitively appealing and vivid than single ‘variables’ – seem to have limited explanatory power when it comes to predicting newcomers’ early integration trajectories.     

Modeling individual migraine severity with autoregressive ordered probit models

This paper considers the problem of modeling migraine severity assessments and their dependence on weather and time characteristics. We take on the viewpoint of a patient who is interested in an individual migraine management strategy. Since factors influencing migraine can differ between patients in number and magnitude, we show how a patient’s headache calendar reporting the severity measurements on an ordinal scale can be used to determine the dominating factors for this special patient. One also has to account for dependencies among the measurements. For this the autoregressive ordinal probit (AOP) model of Müller and Czado (J Comput Graph Stat 14: 320–338, 2005) is utilized and fitted to a single patient’s migraine data by a grouped move multigrid Monte Carlo (GM-MGMC) Gibbs sampler. Initially, covariates are selected using proportional odds models. Model fit and model comparison are discussed. A comparison with proportional odds specifications shows that the AOP models are preferred.     

Smoking risk factors and gender differences among Spanish high school students

The objectives of the present study were to analyze the pattern of tobacco use among Spanish adolescents, as well as to determine gender differences in specific risk factors of cigarette use. The study sample was made up of 1,483 boys and 1,358 girls, aged 12-16 (M = 14). Participants were asked to answer an ad-hoc instrument to evaluate the pattern of use, perceived availability, risk of harm, family- and peer-use, engagement in leisure activities, drive for thinness, and self-esteem. Results showed no gender differences in the pattern of use. With regard to risk and protector factors, a predictive analysis showed that peer-related variables were the most determinant for tobacco use both for boys and girls. Some gender differences were also detected: Playing sports was protective for boys only, and listening to music for girls only. Drive for thinness and self-esteem were not related to tobacco use for either boys or girls. These findings help increase our understanding of smoking risk factors in adolescence and to pay special attention to the group of friends when planning prevention programs to reduce risk factors.     

Characterizing best–worst voting systems in the scoring context

An increasing body of theoretical and empirical work on discrete choice considers a choice design in which a person is asked to select both the best and the worst alternative in an available set of alternatives, in contrast to more traditional tasks, such as where the person is asked to: select the best alternative; select the worst alternative; rank the alternatives. Here we consider voting systems motivated by such “best–worst” choice; characterize a class of “best–worst” voting systems in terms of a set of axioms in the context of scoring rules; and discuss briefly possible extensions to approval–disapproval systems.     

Modeling of Acoustic Signal Energies with a Generalized Frank Copula. A Linguistic Conjecture is Reviewed

In this article a generalized Frank copula was selected to model the dependence between the energy on two frequency bands of the speech signal, coming from eight languages. An algorithm was developed that uses maximum likelihood to choose the best fitting copula’s parameters. Through bootstrap, the algorithm estimates the variability of the parameters for each language and also computes confidence regions by means of Voronoi tesselations. A linguistic conjecture which claims that the languages are organized in three rhythmic classes, was confirmed by the Voronoi regions. Modeling with a uniparametric Frank copula, the different degrees of dependence between the energies were quantified.     

Social support and life satisfaction among gay men in Spain

Since the early 1960s, social support has been a topic of interest and study among social psychologists and other professionals investigating social issues. In spite of this growing interest by the scientific community, there are few studies on social support in the lesbian, gay, bisexual, and transgender (LGBT) community, and even fewer on the impact of social support on life satisfaction. In this regard, in Spain, there are very few psychosocial studies on homosexual groups. In the present study, the authors analyze social support data and life satisfaction in a sample of 220 gay residents of Málaga and Sevilla. The results show that friends are the most important source of overall social support, and that, in the family, sisters provide the most support and contribute to increased life satisfaction. On the other hand, social support had an effect on the level of life satisfaction, although the results indicate that factors associated with homosexual identity are the best predictors of life satisfaction. The implications of these results are discussed as well as potential future research.