Uma caracterização dos imigrantes no distrito de Évora

Uma vez que existe uma grande necessidade de se obter um maior conhecimento das comunidades imigrantes residentes no Distrito, este trabalho tem como principal objectivo caracterizar a população de imigrantes comunitários residentes no distrito de Évora. Em particular, procuramos analisar os casamentos realizados não só entre os não nacionais e portugueses, bem como entre os nãos nacionais entre si. Consideramos os 354 imigrantes que constituem os imigrantes comunitários inscritos legalmente nos Serviços Estrangeiros e Fronteiras de Évora entre 2006 a 2009. Por outro lado, analisamos, para o mesmo período, os casamentos dos imigrantes que casaram com os portugueses num total de 165 indivíduos. Começamos por levar a efeito uma investigação básica de tipo descritivo para uma caracterização dos imigrantes relativamente a diferentes variáveis e investigamos algumas associações entre elas via tabelas de contingência. Refira-se que a maioria dos imigrantes é do sexo feminino, sendo a nacionalidade mais representativa a brasileira. Com base no modelo de regressão de Cox identificamos factores de risco e diferentes perfis associados à rotura do casamento. Mostramos que há evidência estatística para considerar que um menor nível de escolaridade, o pertencer a um país da União Europeia e o ter entrado à procura de trabalho são níveis de factores que aumentam o risco de rotura do casamento. Analisam-se, ainda, de uma forma crítica, a abordagem paramétrica, procurando modelar os dados através dos modelos Exponencial, Weibull, Lognormal e Log-logístico. ABSTRACT: There is a need to obtain a greater understanding of immigrant communities in the district; this work has as main objective to characterize the population of immigrant community residing in the district of Évora. ln particular, we analyze not only marriages between Portuguese and non-nationals, as well as among non-nationals among themselves. We consider the 354 immigrants who are legally registered immigrants in the Community Service of Foreigners and Frontiers of Évora, from 2006 to 2009. Moreover, we analyze, for the same period, the marriages of immigrants who intermarried with the Portuguese for a total of 165 individuals. We start by carrying out a basic descriptive research in order to characterize the immigrants in relation to several variables and investigated some associations between them by contingency tables. It should be noted that most immigrants are women, and the more representative the Brazilian nationality. Based on the Cox regression model, were possible to identify risk factors and identify profiles of high and low risk associated with the rupture of the marriage. We show that there is statistical evidence to conclude that a less educated levels, belonging to a country inside the European Union and have gone looking for work are factors that increase the risk of rupture of the marriage. The parametric approach is analyzed also, in a critical way, seeking to model the data using exponential, Weibull, Lognormal and Log-logistic.

Obtaining environmental favourability functions from logistic regression

Logistic regression is a statistical tool widely used for predicting species’ potential distributions starting from presence/absence data and a set of independent variables. However, logistic regression equations compute probability values based not only on the values of the predictor variables but also on the relative proportion of presences and absences in the dataset, which does not adequately describe the environmental favourability for or against species presence. A few strategies have been used to circumvent this, but they usually imply an alteration of the original data or the discarding of potentially valuable information. We propose a way to obtain from logistic regression an environmental favourability function whose results are not affected by an uneven proportion of presences and absences. We tested the method on the distribution of virtual species in an imaginary territory. The favourability models yielded similar values regardless of the variation in the presence/absence ratio. We also illustrate with the example of the Pyrenean desman’s (Galemys pyrenaicus) distribution in Spain. The favourability model yielded more realistic potential distribution maps than the logistic regression model. Favourability values can be regarded as the degree of membership of the fuzzy set of sites whose environmental conditions are favourable to the species, which enables applying the rules of fuzzy logic to distribution modelling. They also allow for direct comparisons between models for species with different presence/absence ratios in the study area. This makes themmore useful to estimate the conservation value of areas, to design ecological corridors, or to select appropriate areas for species reintroductions.