Bayes and empirical bayes estimation of the probability that z > x + y

Let X, Y and Z be independent random variables with common unknown distribution F. Using the Dirichlet process prior for F and squared erro loss function, the Bayes and empirical Bayes estimators of the parameters λ(F). the probability that Z > X + Y, are derived. The limiting Bayes estimator of λ(F) under some conditions on the parameter of the process is shown to be asymptotically normal. The aysmptotic optimality of the empirical Bayes estimator of λ(F) is established. When X, Y and Z have support on the positive real line, these results are derived for randomly right censored data. This problem relates to testing whether than used discussed by Hollander and Proshcan (1972) and Chen, Hollander and Langberg (1983).     

Efficient generation of random vectors by using the ratio-of-uniforms method with ellipsoidal envelopes

Stochastic simulation is widely used to validate procedures and provide guidance for both theoretical and practical problems. Random variate generation is the basis of stochastic simulation. Applying the ratio-of-uniforms method to generate random vectors requires the ability to generate points uniformly in a suitable region of the space. Starting from the observation that, for many multivariate distributions, the multidimensional objective region can be covered by a hyper-ellipsoid more tightly than by a hyper-rectangle, a new algorithm to generate from multivariate distributions is proposed. Due to the computational saving it can produce, this method becomes an appealing statistical tool to generate random vectors from families of standard and nonstandard multivariate distributions. It is particularly interesting to generate from densities known up to a multiplicative constant, for example, from those arising in Bayesian computation. The proposed method is applied and its efficiency is shown for some classes of distributions.     

Union Formation Implications of Race and Gender Gaps in Educational Attainment: The Case of Latin America

We use census microdata to assess the levels of educational homogamy in six Latin American countries: Argentina, Brazil, Chile, Costa Rica, Ecuador and Mexico. This paper contributes to the literature on homogamy in three ways. First, by conducting a comparative analysis between countries belonging to the still little-studied region of Latin America, which is still undergoing intense and varied processes of demographic, economic, social, and political modernization. Second, by simultaneously including variables of structural and individual nature. Finally, by making progress with respect to the interactions between educational homogamy and other important variables associated with high levels of social inequality in the region: race, ethnicity and birthplace.     

Investigating the impact of Hurricane Maria on an ongoing birth cohort in Puerto Rico

Population and Environment - Prior to Hurricane Maria, Puerto Rico already had 200+ hazardous waste sites, significant contamination of water resources, and among the highest rates of preterm birth...     

Evaluating Lightning-Caused Fire Occurrence Using Spatial Generalized Additive Models: A Case Study in Central Spain

It is widely accepted that the relationship between lightning wildfire occurrence and its influencing factors vary depending on the spatial scale of analysis, making the development of models at the regional scale advisable. In this study, we analyze the effects of different biophysical variables and lightning characteristics on lightning-caused forest wildfires in Castilla y León region (Central Spain). The presence/absence of at least one lightning-caused fire in any 4 × 4-km grid cell was used as a dependent variable and vegetation type and structure, terrain, climate, and lightning characteristics were used as possible covariates. Five prediction methods were compared: a generalized linear model (GLM), a random forest model (RFM), a generalized additive model (GAM), a GAM that includes a spatial trend function (GAMs) and a spatial autoregressive model (AUREG). A GAMs with just one covariate, apart from longitude and latitude for each observation included as a combined effect, was considered the most appropriate model in terms of both predictive ability and simplicity. According to our results, the probability of a forest being affected by a lightning-caused fire is positively and nonlinearly associated with the percentage of coniferous woodlands in the landscape, suggesting that occurrence is more closely associated with vegetation type than with topography, climate, or lightning characteristics. The selected GAMs is intended to inform the Regional Government of Castilla y León (the fire and fuel agency in the region) regarding identification of areas at greatest risk so it can design long-term forest fuel and fire management strategies.     

Flora of the tram tracks of Bratislava

Urban Ecosystems - Tram and railway tracks represent specific urban habitats, which host a specific type of flora. This study aims to compile the information about species composition of flora of...     

Convex partitions with 2-edge connected dual graphs

It is shown that for every finite set of disjoint convex polygonal obstacles in the plane, with a total of n vertices, the free space around the obstacles can be partitioned into open convex cells whose dual graph (defined below) is 2-edge connected. Intuitively, every edge of the dual graph corresponds to a pair of adjacent cells that are both incident to the same vertex.     

Beyond Hidden Figures: Shining a Spotlight on Constructed Hierarchies of Gender,Age, and Elementary Mathematics

Gender Issues - This article focuses on conversations about gender and mathematics among other intersecting identities such as age, education level, and professional expertise. I used positioning...     

The guaranteed minimum income in Portugal: A universal safety net under political and financial pressure

The Guaranteed Minimum Income (GMI) was created in Portugal by a centre-left Socialist Party government in 1996, as the most important constitutive part of a ‘new generation of active social policies,’ which completed the existence in Portugal of a universal system of guaranteed income. Its transformation into a Social Integration Income (SII) in 2003 and its retrenchment in the period of the Great Recession and troika austerity (2011–2015) has reduced the scope of this policy measure as a universal safety net policy. This article examines the context and the major drivers for the creation and for the policy changes that occurred in the GMI/SII. Looking at the political debates and the changes in this policy measure along this period, we argue that the major reforms introduced since its creation reflect ideological cleavages within the political arena. Considering the very low share in total government current expenditure of GMI/SII, this can explain the social policy selective retreat associated to the changes introduced in this policy measure by the centre-right coalition in government, in the latest period of cost containment of social policy in Portugal, leading to a great decrease in the number of beneficiaries and to an increase of its inadequacy.     

An extension of the discrete Lindley distribution with applications

An extension of the discrete Lindley distribution is obtained by discretizing the continuous failure rate model in the generalized continuous distribution in Zakerzadeh and Dolati [Zakerzadeh, Y., & Dolati, A. (2009). Generalized Lindley distribution. Journal of Mathematical Extension, 3(2), 13–25]. The result is a generalization of the geometric distribution which presents high versatility since covariates can be included in the model.