Homogeneity test for functional data

In the context of functional data analysis, we propose new sample tests for homogeneity. Based on some well-known depth measures, we construct four different statistics in order to measure distance between the two samples. A simulation study is performed to check the efficiency of the tests when confronted with shape and magnitude perturbation. Finally, we apply these tools to measure the homogeneity in some samples of real data, and we obtain good results using this new method.     

Bimodal symmetric-asymmetric power-normal families

This article proposes new symmetric and asymmetric distributions applying methods analogous as the ones in Kim (2005 Kim, H.J. (2005). On a class of two-piece skew-normal distributions. Statist.: J. Theoret. Appl. Statist. 39:537–553.[Taylor &; Francis Online], [Web of Science ®] , [Google Scholar]) and Arnold et al. (2009 Arnold, B.C., H.W. Gómez, and H.S. Salinas. (2009). On multiple constraint skewed models. Statist. J. Theoret. Appl. Statist. 43: 279–293.[Taylor &; Francis Online], [Web of Science ®] , [Google Scholar]) to the exponentiated normal distribution studied in Durrans (1992 Durrans, S.R. (1992). Distributions of fractional order statistics in hydrology. Water Resour. Res. 28:1649–1655.[Crossref], [Web of Science ®] , [Google Scholar]), that we call the power-normal (PN) distribution. The proposed bimodal extension, the main focus of the paper, is called the bimodal power-normal model and is denoted by BPN(α) model, where α is the asymmetry parameter. The authors give some properties including moments and maximum likelihood estimation. Two important features of the model proposed is that its normalizing constant has closed and simple form and that the Fisher information matrix is nonsingular, guaranteeing large sample properties of the maximum likelihood estimators. Finally, simulation studies and real applications reveal that the proposed model can perform well in both situations.     

Random spectral measure for non Gaussian moving averages

We study the distribution of phases and amplitudes for the spectral representation of weighted moving averages of a general noise measure. The simple independent structure, known for the Gaussian case, and involving Rayleigh amplitude and uniform phase distributions, is lost for the non Gaussian noise case. We show that the amplitude/phase distributions exhibit a rich and more complex structure depending not just on the covariance of the process but specifically on the form of the kernel and the noise distribution. We present a theoretical tool for studying these distributions that follows from a proof of the spectral theorem that yields an explicit expression for the spectral measure. The main interest is in noise measures based on second-order Lévy motions since such measures are easily available through independent sampling. We approximate the spectral stochastic measure by independent noise increments which allows us to obtain amplitude/phase distributions that is of fundamental interest for analyzing processes in the frequency domain. For the purpose of approximating the moving average process through sums of trigonometric functions, we assess the mean square error of discretization of the spectral representation. For a specified accuracy, the approximation is explicitly given. We illustrate the method for the moving averages driven by the Laplace motion.     

Bayesian non-parametric modeling for integro-difference equations

Integro-difference equations (IDEs) provide a flexible framework for dynamic modeling of spatio-temporal data. The choice of kernel in an IDE model relates directly to the underlying physical process modeled, and it can affect model fit and predictive accuracy. We introduce Bayesian non-parametric methods to the IDE literature as a means to allow flexibility in modeling the kernel. We propose a mixture of normal distributions for the IDE kernel, built from a spatial Dirichlet process for the mixing distribution, which can model kernels with shapes that change with location. This allows the IDE model to capture non-stationarity with respect to location and to reflect a changing physical process across the domain. We address computational concerns for inference that leverage the use of Hermite polynomials as a basis for the representation of the process and the IDE kernel, and incorporate Hamiltonian Markov chain Monte Carlo steps in the posterior simulation method. An example with synthetic data demonstrates that the model can successfully capture location-dependent dynamics. Moreover, using a data set of ozone pressure, we show that the spatial Dirichlet process mixture model outperforms several alternative models for the IDE kernel, including the state of the art in the IDE literature, that is, a Gaussian kernel with location-dependent parameters.     

Automatic specification of piecewise linear additive models: application to forecasting natural gas demand

When facing any forecasting problem not only is accuracy on the predictions sought. Also, useful information about the underlying physics of the process and about the relevance of the forecasting variables is very much appreciated. In this paper, it is presented an automatic specification procedure for models that are based on additivity assumptions and piecewise linear regression. This procedure allows the analyst to gain insight about the problem by examining the automatically selected model, thus easily checking the validity of the forecast. Monte Carlo simulations have been run to ensure that the model selection procedure behaves correctly under weakly dependent data. Moreover, comparison over other well-known methodologies has been done to evaluate its accuracy performance, both in simulated data and in the context of short-term natural gas demand forecasting. Empirical results show that the accuracy of the proposed model is competitive against more complex methods such as neural networks.     

“Nothing goes as planned”: Practitioners reflect on matching children and foster families

Matching children with foster carers is an important step in every nonkinship family foster care placement. Although guidelines for matching are provided in several studies, the case‐specific context of the decision can influence the practitioners' ability to adhere to these guidelines. Therefore, this study answers the following question: “How does the case‐specific context influence the practitioners' decision‐making process regarding matching in family foster care?” Using a qualitative design, 20 semistructured interviews were conducted with practitioners matching children with foster families. Three themes emerged representing different layers of practitioners' everyday decision‐making: matching as planned, matching being tailored, and matching being compromised. The results show that exceptions are part of practitioners' daily work, either due to the belief that it might benefit those involved or because of obstacles presented during the decision‐making process. When the decision is compromised, matching practitioners lower their standards, while at the same time safeguarding the quality of the match. This proves that matching in practice is more than choosing a family, and guidelines are needed to determine what “good‐enough” matching should entail.     

Corporate and managerial characteristics as drivers of social responsibility disclosure by state-owned enterprises

The public administration sector, including state owned enterprises (SOEs), has developed various types of information disclosure practice, in response to stakeholders’ demands, in parallel with developments in the private sector. This paper analyses the corporate social responsibility (CSR) information disclosed by SOEs and the influence exerted by the characteristics of the SOEs themselves (size, industry sector, degree of government ownership and number of years in operation) and by those of their managers (age, gender, CSR education profile and CSR responsibilities in the workplace). To do so, an index of CSR information disclosure was created, based on the responses made to a questionnaire in this respect. An empirical regression model was then applied to test and categorise the factors analysed. According to the results obtained, the size and sector of the SOE, together with the manager’s CSR responsibilities, are the factors that most significantly affect the online disclosure of CSR information.     

A spatial randomness test based on the box-counting dimension

AStA Advances in Statistical Analysis - Statistical modelling of a spatial point pattern often begins by testing the hypothesis of spatial randomness. Classical tests are based on quadrat counts...     

Language in the process of labour market rationalisation: A sociohistorical approach across twentieth-century Spain

This article analyses the role of linguistic skills in the process of defining professional classifications in Spain during 1919–1980. The aim is to determine the social evaluation of the skills involved. To retrace the classifications, a total of 114 official documents were examined, establishing a chronological division into three major stages: 1920–1940, 1940–1960 and 1960–1980. The first period (1920–1940) shows efforts toward the initial objectification of working conditions and salary scales, revealing social prejudices and tacit conventions shaping the employment hierarchy, while the second one (1940–1960) indicates the extent to which office work stood out over manual work. Finally, the third stage (1960–1980) shows processes of language rationalisation, which entailed attempts to standardise positions based on required skill sets.     

Improving the protection of migrant workers with work histories in the European Union and Ibero-America: Enhancing the coordination of international social security instruments

Migration affects almost every nation, emphasizing the need to guarantee social security rights for all migrants and their families. This article focuses on the rights of workers who migrate between the countries of the European Union (EU) and the Ibero-American community. In the EU, social security systems are increasingly coordinated through Regulation No. 883/2004 and its Implementing Regulation No. 987/2009. In the Ibero-American community, coordination is sought through the Ibero-American Social Security Convention. Despite convergence between these two international instruments, coordination is still lacking between them. This article presents a comparative analysis to articulate the necessary mechanisms to guarantee coordination, to respect the social security rights of migrant workers. We focus on the cooperation and coordination between regional as well as national systems, specifically looking at the need for and aims of a rapprochement between these two major international coordination instruments to provide greater EU-Ibero-American cooperation. Finally, the importance of promoting greater international cooperation in social security policy and administration is highlighted, to engender the adequate protection of the rights as well as the free movement of migrant workers.