Identifiability and Comparison of Estimation Methods on Weibull Mixture Models

In this article, the finite mixture model of Weibull distributions is studied, the identifiability of the model with m components is proven, and the parameter estimators for the case of two components resulted by several algorithms are compared. The parameter estimators are obtained with maximum likelihood performing calculations with different algorithms: expectation-maximization (EM), Fisher scoring, backfitting, optimization of k-nearest neighbor approach, and random walk algorithm using Monte Carlo simulation. The Akaike information criterion and the log-likelihood value are used to compare models. In general, the proposed random walk algorithm shows better performance in mean square error and bias. Finally, the results are applied to electronic component lifetime data.     

Divorce and the business cycle: a cross-country analysis

In this paper, we examine the role of the business cycle in divorce. To do so, we use a panel of 29 European countries covering the period from 1991 to 2012. We find the unemployment rate negatively affects the divorce rate, pointing to a pro-cyclical evolution of the divorce rate, even after controlling for socio-economic variables and unobservable characteristics that can vary by country, and/or over time. Results indicate that a one-percentage-point increase in the unemployment rate involves almost 0.025 fewer divorces per thousand inhabitants. The impact is small, representing around 1.2 % of the average divorce rate in Europe during the period considered. Supplementary analysis, developed to explore a possible non-linear pattern, confirms a negative relationship between unemployment and divorce in European countries, with the inverse relationship being more pronounced in those countries with higher divorce rates.     

The impact of modular platforms on automobile manufacturing networks

This paper explores the impact on automobile manufacturing networks of adopting modular platforms to replace the standard platforms used to date. Analysis of European manufacturers’ production networks shows that the use of modular architecture improves coordination by increasing manufacturing mobility and thriftiness ability. The changes resulting from this new modular approach also allow manufacturing capacity to be reorganised and overcapacity to be partially eliminated. From the point of view of production systems, the adaptation of manufacturing processes and facilities to this new architecture should aim to increase flexibility by integrating production around a single platform, allowing for different dimensions and for a larger number of models to be produced in a single plant.     

Subjective well‐being: what do adolescents say?

The aim of this paper is to analyse how 10‐ to 15‐year‐old adolescents define their own perceptions of well‐being and the factors influencing it at their age. Ten focus groups were organized, two from each age group. One group for each age included the students with the lowest scores in subjective well‐being (SWB) and the other included those with the highest, according to their responses to previously administered psychometric scales. The views of the participating adolescents were explored by means of a content analysis. In general, the children mentioned both positive and negative elements of participating in defining what constitutes well‐being. According to these children, well‐being is related to both affects and attitudes, relations with family and friends being key factors in it. Differences in the information provided reveal some variations according to age and SWB score. Children scoring lower in SWB tend to refer more to relationships with friends and basic needs covered, whereas those scoring higher tend to refer more to family relationships and not having problems. The results of this research can contribute to both social policy design and appraisal as they provide an in‐depth understanding of how SWB works at these ages.     

The Values Adolescents Aspire to,Their Well-being and the Values Parents Aspire to for Their Children

This paper presents a study of the relationship between the psychological well-being of Spanish adolescents from 12 to 16 years old and the values they aspire to for the future (N = 1,618). Adolescents’ well-being is explored through (a) their satisfaction with 19 specific life domains, (b) the Personal Well-Being Index (Cummins, Social Indicators Research, 43, 307−334, 1998) and (c) an item on overall satisfaction with life. The values they aspire to are explored by means of a list of 23 personal qualities or values. Satisfaction domains and values aspired to have been grouped into dimensions using principal component analysis (PCA). Boys scored significantly higher on the materialistic values dimension and the capacities and knowledge related values dimension, while girls scored higher on the interpersonal relationship related values dimension. The youngest adolescents scored higher on materialistic values, while the oldest scored higher on interpersonal relationships related values. Such results are similar to those obtained in a previous study, using a shorter version of the lists of satisfaction domains and of values aspired to and a sample of 8,995 adolescents and 4,381 of their parents from five different countries. In both studies results suggest that values aspired to can be considered a well-being related construct. However, an important change appears in the latest Spanish sample: Family values no longer fit with the interpersonal relationships related values dimension in the PCA, and now function as a separate value dimension which shows no correlation with overall life satisfaction, the PWI, or life satisfaction domains with the exception of family satisfaction. Interestingly, family values have also changed their loading dimension in the PCA developed with the answers from a sample of parents about the values they aspire to for their own child’s future (N = 723). Parents’ responses were compared with those of their own child, with concordances observed in about half of the families, low discrepancies in about one third and high or very high discrepancies in about 20%. Although the results of this study have their limitations, they suggest support for the hypothesis that important changes in values aspired to may be taking place over a short period of time, consistent with the findings of changes in values in several countries (Inglehart, Modernization and postmodernization. Cultural, economic and political change in 43 societies, Princeton: Princeton University Press, 1997), but apparently with no outstanding impact on adolescents’ well-being.     

Sexual prejudice among Puerto Rican young adults

Sexual prejudice is linked to hate crimes, mental health, risk behaviors, and stigma. Few studies have examined sexual prejudice among Latinos. We surveyed 382 college students in Puerto Rico. A structural model tested whether contact and positive experiences with homosexuals, perceived similarities with peers' attitudes toward homosexuality, and religiosity were predictive of sexual prejudice among Puerto Rican young adults. Sex differences in the structural model were explored. With the exception of peers' attitudes toward homosexuality, all study variables predict sexual prejudice. No sex differences were found. Implications for decreasing sexual prejudice among Puerto Rican youth in a college setting are discussed.     

Different Factors for Different Causes: Analysis of the Spatial Aggregations of Fire Ignitions in Catalonia (Spain)

The present study analyzes the effects of different socioeconomic factors on the frequency of fire ignition occurrence, according to different original causes. The data include a set of documented ignition points in the region of Catalonia for the period 1995–2008. The analysis focused on the spatial aggregation patterns of the ignitions for each specific ignition cause. The point‐based data on ignitions were interpolated into municipality‐level information using kernel methods as the basis for defining five ignition density levels. Afterwards, the combination of socioeconomic factors influencing the ignition density levels of the municipalities was analyzed for each documented cause of ignition using a principal component analysis. The obtained results confirmed the idea that both the spatial aggregation patterns of fire ignitions and the factors defining their occurrence were specific for each of the causes of ignition. Intentional fires and those of unknown origin were found to have similar spatial aggregation patterns, and the presence of high ignition density areas was related to high population and high unemployment rates. Additionally, it was found that fires originated from forest work, agricultural activities, pasture burning, and lightning had a very specific behavior on their own, differing from the similarities found on the spatial aggregation of ignitions originated from smokers, electric lines, machinery, campfires, and those of intentional or unknown origin.     

Shapiro–Wilk test for skew normal distributions based on data transformations

A probability property that connects the skew normal (SN) distribution with the normal distribution is used for proposing a goodness-of-fit test for the composite null hypothesis that a random sample follows an SN distribution with unknown parameters. The random sample is transformed to approximately normal random variables, and then the Shapiro–Wilk test is used for testing normality. The implementation of this test does not require neither parametric bootstrap nor the use of tables for different values of the slant parameter. An additional test for the same problem, based on a property that relates the gamma and SN distributions, is also introduced. The results of a power study conducted by the Monte Carlo simulation show some good properties of the proposed tests in comparison to existing tests for the same problem.     

A Condition to Obtain the Same Decision in the Homogeneity Testing Problem from the Frequentist and Bayesian Point of View

We develop a Bayesian procedure for the homogeneity testing problem of r populations using r × s contingency tables. The posterior probability of the homogeneity null hypothesis is calculated using a mixed prior distribution. The methodology consists of choosing an appropriate value of π₀ for the mass assigned to the null and spreading the remainder, 1 ? π₀, over the alternative according to a density function. With this method, a theorem which shows when the same conclusion is reached from both frequentist and Bayesian points of view is obtained. A sufficient condition under which the p-value is less than a value α and the posterior probability is also less than 0.5 is provided.