Simulation-based model comparison methodology with application to road accident models

This article assumes the goal of proposing a simulation-based theoretical model comparison methodology with application to two time series road accident models. The model comparison exercise helps to quantify the main differences and similarities between the two models and comprises of three main stages: (1) simulation of time series through a true model with predefined properties; (2) estimation of the alternative model using the simulated data; (3) sensitivity analysis to quantify the effect of changes in the true model parameters on alternative model parameter estimates through analysis of variance, ANOVA. The proposed methodology is applied to two time series road accident models: UCM (unobserved components model) and DRAG (Demand for Road Use, Accidents and their Severity). Assuming that the real data-generating process is the UCM, new datasets approximating the road accident data are generated, and DRAG models are estimated using the simulated data. Since these two methodologies are usually assumed to be equivalent, in a sense that both models accurately capture the true effects of the regressors, we are specifically addressing the modeling of the stochastic trend, through the alternative model. Stochastic trend is the time-varying component and is one of the crucial factors in time series road accident data. Theoretically, it can be easily modeled through UCM, given its modeling properties. However, properly capturing the effect of a non-stationary component such as stochastic trend in a stationary explanatory model such as DRAG is challenging. After obtaining the parameter estimates of the alternative model (DRAG), the estimates of both true and alternative models are compared and the differences are quantified through experimental design and ANOVA techniques. It is observed that the effects of the explanatory variables used in the UCM simulation are only partially captured by the respective DRAG coefficients. This a priori, could be due to multicollinearity but the results of both simulation of UCM data and estimating of DRAG models reveal that there is no significant static correlation among regressors. Moreover, in fact, using ANOVA, it is determined that this regression coefficient estimation bias is caused by the presence of the stochastic trend present in the simulated data. Thus, the results of the methodological development suggest that the stochastic component present in the data should be treated accordingly through a preliminary, exploratory data analysis.     

Validating the Portuguese Version of the Satisfaction With Life Scale in an Elderly Sample

Life satisfaction is referred to a cognitive, judgmental process (Diener et al. in J Pers Assess 49:71–75, 1985), in which person’s quality of life is globally assessed according to his/her chosen criteria (Shin and Johnson in Soc Indic res 5:475–492, 1978). Thus, life satisfaction is a conscious cognitive judgment, based on the comparison of one’s life with a self-imposed standard or set of standards, which lead to a global assessment of life (Pavot and Diener in Psychol Assess 5:164–172, 1993). Among the many scales developed to measure life satisfaction, the Satisfaction With Life Scale (SWLS, Diener et al. in J Pers Assess 49:71–75, 1985) is one of the global life satisfaction scales more often used in the research arena. It is composed of five items assessing global life satisfaction, using a Likert type response format. The aim of this paper is to validate the Portuguese version of the SWLS via confirmatory factor analysis, with a sample of 1,003 elderly from Angola. Reliability, factorial and criterial validity estimates are presented. Overall, the results shown that the scale had an adequate one-factor confirmatory solution, satisfying reliability indices, and adequate criterion-related validity when assessed in a sample of Angolan elderly. The discussion relates the results with existing literature and posits the contributions of the paper: firstly, it offers the researchers on life satisfaction in Portuguese-speaking contexts a brief, self-rated measure of satisfaction with life that has sound psychometric properties, validity, and reliability; secondly, it is the first confirmatory validation of the scale in Portuguese.     

Book reviews

Academics and others have long made use of survey items framed in a Likert form. This type of question, where respondents are asked to agree or disagree with a series of statements, has long been a staple of those creating attitude scales. There has, however, been increasing use of these items in inappropriate settings. This article discusses the appropriate and inappropriate use of Likert items in social science research, using three settings where the agree-disagree response settings are wrongly applied. It concludes with speculation about the diffusion of this form throughout the research culture.     

Pleasure Principles: Reflections on Saketopoulou’s “To Suffer Pleasure”

In this essay I elaborate some of the seminal ideas in Saketopoulou’s article ‘To Suffer Pleasure,” contrast them to Foucault’s notion of technologies of the self, and consider the uses of psychic work and physical pleasure. I highlight the importance Saketopoulou makes of a corporeal solution to intergenerational conflicts and consider ego shattering as a site of encounter: with the limits of signification in the body and its emergence at the edge of the social.     

Comentarios a «accióninvestigación y problemas de las minorias»

Resumen

Hemos realizado un estudio diferencial sobre las interpretaciones causales y sus consecuencias cognitivo- afectivas en un contexto de robo, utilizando como marco teórico el último modelo atribucional de Weiner (1986). Para ello, hemos aplicado cuestionarios de autoinforme a 1.450 sujetos menores de edad. Los resultados, obtenidos mediante análisis de la varianza y técnicas de regresión, indican (1) que existe una taxonomía de las causas claramente diferenciada en función de las dimensiones—locus, estabilidad y controlabilidad—, y de la perspectiva—actor/observador—de los sujetos; (2) que la estabilidad de las causas determina la predicción de reincidencia, y que ésta es mayor en los sujetos que dicen haber cometido más robos, y (3) que el sentimiento de culpa está determinado por la controlabilidad de las causas y varía como función inversa de la experiencia delictiva. Finalmente, señalamos algunas implicaciones teóricas y aplicadas de este trabajo.     

Costs of Extending the Noncontributory Pension Program for Elderly: The Mexican Case

Population aging coupled with high poverty rates among older persons and a lack of access to social-security benefits or traditional support systems have led governments in low and middle-income countries to introduce non-contributory pension programs for the elderly. This article reviews a non-contributory pension program introduced in Mexico in 2007 that has since expanded greatly. We use a variety of sources to estimate current and future costs of this program.     

Skew-normal distribution for growth curve models in presence of a heteroscedasticity structure

In general, growth models are adjusted under the assumptions that the error terms are homoscedastic and normally distributed. However, these assumptions are often not verified in practice. In this work we propose four growth models (Morgan–Mercer–Flodin, von Bertalanffy, Gompertz, and Richards) considering different distributions (normal, skew-normal) for the error terms and three different covariance structures. Maximum likelihood estimation procedure is addressed. A simulation study is performed in order to verify the appropriateness of the proposed growth curve models. The methodology is also illustrated on a real dataset.