A method for K-Means seeds generation applied to text mining

In this paper, a methodology is proposed in order to produce a set of seeds later used as a starting point to K-Means-type unsupervised classification algorithms for text mining. Our proposal involves using the eigenvectors obtained from principal component analysis to extract initial seeds, upon appropriate treatment for search of lightly overlapping clusters which are also clearly identified by keywords. This work is motivated by the interest of the authors in the problem of identification of topics and themes previously unknown in short texts. Therefore, in order to validate the goodness of this method, it was applied on a sample of labeled e-mails (NG20) representing a gold standard within the field of text mining. Specifically, some corpora referenced in the literature have been used, configured in accordance to a mix of topics contained in the sample. The proposed method improves on the results of other state-of-the-art methods to which it is compared.     

Non-parametric Sampling Approximation via Voronoi Tessellations

In this article we propose a novel non-parametric sampling approach to estimate posterior distributions from parameters of interest. Starting from an initial sample over the parameter space, this method makes use of this initial information to form a geometrical structure known as Voronoi tessellation over the whole parameter space. This rough approximation to the posterior distribution provides a way to generate new points from the posterior distribution without any additional costly model evaluations. By using a traditional Markov Chain Monte Carlo (MCMC) over the non-parametric tessellation, the initial approximate distribution is refined sequentially. We applied this method to a couple of climate models to show that this hybrid scheme successfully approximates the posterior distribution of the model parameters.     

Assessing the predictive value of a binary surrogate for a binary true endpoint based on the minimum probability of a prediction error

The individual causal association (ICA) has recently been introduced as a metric of surrogacy in a causal‐inference framework. The ICA is defined on the unit interval and quantifies the association between the individual causal effect on the surrogate (ΔS) and true (ΔT) endpoint. In addition, the ICA offers a general assessment of the surrogate predictive value, taking value 1 when there is a deterministic relationship between ΔT and ΔS, and value 0 when both causal effects are independent. However, when one moves away from the previous two extreme scenarios, the interpretation of the ICA becomes challenging. In the present work, a new metric of surrogacy, the minimum probability of a prediction error (PPE), is introduced when both endpoints are binary, ie, the probability of erroneously predicting the value of ΔT using ΔS. Although the PPE has a more straightforward interpretation than the ICA, its magnitude is bounded above by a quantity that depends on the true endpoint. For this reason, the reduction in prediction error (RPE) attributed to the surrogate is defined. The RPE always lies in the unit interval, taking value 1 if prediction is perfect and 0 if ΔS conveys no information on ΔT. The methodology is illustrated using data from two clinical trials and a user‐friendly R package Surrogate is provided to carry out the validation exercise.     

Spanish adaptation of the Antifat Attitudes Scale / Adaptación al castellano de la Escala de Actitud Antiobesos

Antifat attitudes may be defined as the negative assessment of people with weight problems. To evaluate them, the Antifat Attitudes Scale (AFA) has been used in most studies. The aim of this study is to adapt the AFA questionnaire to the Spanish population. The sample was made up of 1,457 university students from all over Spain. Exploratory and confirmatory factor analyses showed that the items on the questionnaire fit a three-factor model corresponding to the three dimensions proposed by the original author (dislike, fear of fat and willpower) and that they are interrelated. In light of these results, we conclude that the questionnaire is methodologically valid and can be used by the scientific community to measure antifat attitudes.     

<Emphasis Type="Bold">Increasing Inequality in Parent Incomes and Children’s Schooling</Emphasis>

Income inequality and the achievement test score gap between high- and low-income children increased dramatically in the United States beginning in the 1970s. This article investigates the demographic (family income, mother’s education, family size, two-parent family structure, and age of mother at birth) underpinnings of the growing income-based gap in schooling using data from the Panel Study of Income Dynamics. Across 31 cohorts, we find that increases in the income gap between high- and low-income children account for approximately three-quarters of the increasing gap in completed schooling, one-half of the gap in college attendance, and one-fifth of the gap in college graduation. We find no consistent evidence of increases in the estimated associations between parental income and children’s completed schooling. Increasing gaps in the two-parent family structures of high- and low-income families accounted for relatively little of the schooling gap because our estimates of the (regression-adjusted) associations between family structure and schooling were surprisingly small for much of our accounting period. On the other hand, increasing gaps in mother’s age at the time of birth accounts for a substantial portion of the increasing schooling gap: mother’s age is consistently predictive of children’s completed schooling, and the maternal age gap for children born into low- and high-income families increased considerably over the period.     

Ergonomics and usability of children interfaces: Spore®, the case study

This study supports itself in ergonomic concepts and usability criteria by prioritizing the identification and correction of problems found during the interaction of children with projected interfaces for them and left from the cognitive, interactional and interfacial difficulties caused by the excesses of color, elements and animation in sites and games, between them the difficulty of recognition of the information during the interaction with the elements of grid of the interface. The results of the methodology had proven that 78.38% of the 37 children got so absorbed by the game and forgot to fulfill their tasks, at least partially, and that the application of the supported ergonomic beddings in usability criteria is imperative. It is relevant to point out that the projetual activity of the game is centered in the user, the child, whose behavior is distinct and particular. Points that had been disclosed that had passed unobserved by the involved adults in this project, and that they had displayed the unappropriateness of some screens of the Spore? to the etária band due to the ambiguity of the game, besides, the children had been sensible to the clarity in some screens and had passed for unnecessary situations of stress.