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The objective of this study was to analyze the effect of motor play on the emotions of boys and girls of ESO and secondary school, in a phase of emotional awareness acquisition. A total of 183 students from four regions of Spain participated, aged between 12 and 17 years old. Eight intervention sessions were held (two sessions for each type of game). After the practice of the games, the participants valued their emotional experience from one to ten responding to the validated GES questionnaire. For the analysis of the data, two different but complementary statistical techniques were applied: generalized estimation equations and classification and regression trees. Among the main findings the following ones stand out: a) the role of motor play as a pedagogical resource to generate positive emotions and promote the development of motor and socio-emotional skills; b) the physical education teacher should consider in their interventions the type of relationships that occur in games and their effects on emotions; c) the effect of sociomotor games on the positive emotions of boys and girls, especially opposition games. [ABSTRACT FROM AUTHOR]

The degree of contamination of a site, due to the deposition of mercury from mine tailings, is directly related to soil properties since these determine the mobility of pollutants. The objective of this work was to determine the relationship between soil properties and total mercury, using classification and regression tree analysis, and geostatistical methods. A total of 102 samples were collected to measure total mercury and 10 soil-properties analysis. The regression analysis with decision trees showed four relationships between total mercury and chemical properties: 1) pH > 8.5: total mercury > 64 mg/kg; 2) organic matter > 5.5%: total mercury > 19 mg/kg; 3) bicarbonates > 256 mg/kg: total mercury > 77 mg/kg; and 4) redox potential > 171 mV: total mercury < 49 mg/kg. In addition, a relationship was found between the regression decision trees and the maps elaborated with the geostatistical methods. For example, in places with higher concentrations of total mercury, there is a greater amount of organic matter, pH, and bicarbonates; however, there was higher redox potential in the lower concentrations of total mercury. In conclusion 1) high organic matter contents favor the retention of mercury, 2) neutral- alkaline pH favors low mobility of mercury, 3) bicarbonates favors mercury stabilization, and 4) intermediate redox potential provides soil stability to mercury pollution. [ABSTRACT FROM AUTHOR]

This paper identifies factors that explain the survival of Argentine trade flows using the combination of the Classification And Regression Tree analysis (CART) method and cross-section econometrics as the identification method. While the first determines the best predictors, the second offers a global function that links the dependent variable with those. The combination of these methods allows to reduce the number of potentially explanatory variables in problems in which there is no theoretical consensus, or to resolve situations in which there are non-linear relationships, missing data or anomalous observations. The application to the case study allows us to observe that there is a significant difference between pre-existing export flows and new flows, even though the explanatory variables of their duration turn out to be the same. [ABSTRACT FROM AUTHOR]

Since the start of the PISA evaluations there have been numerous studies that have metaphorically tried «to separate the gold from the sand», in other words, to derive useful knowledge to guide educational practice and policy from the vast amount of data collected. However, research that uses data mining techniques to extract knowledge from the databases provided by the OECD has been less common. This paper analyses the context questionnaires from a metric perspective using a methodology based on data mining with «regression trees». Its main goal is to discover how much value (how much «gold») is in the items that compose these questionnaires, considering their use as predictors of the performance of Spanish students. The results provide a list of the items selected in the six questionnaires and their predictive value. It also provides a methodological approach to help improve the productivity of educational research derived from PISA. [ABSTRACT FROM AUTHOR]