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During the last 10 years different interpretative methods for analysing the effect or importance of input variables on the output of a feedforward neural network have been proposed. These methods can be grouped into two sets: analysis based on the magnitude of weights; and sensitivity analysis. However, as described throughout this study, these methods present a series of limitations. We have defined and validated a new method, called Numeric Sensitivity Analysis (NSA), that overcomes these limitations, proving to be the procedure that, in general terms, best describes the effect or importance of the input variables on the output, independently of the nature (quantitative or discrete) of the variables included. The interpretative methods used in this study are implemented in the software program Sensitivity Neural Network 1.0, created by our team.

The aim of this study was to investigate the relationships between math background, trait anxiety, test anxiety, statistics anxiety, attitudes toward statistics and statistics performance in a sample of 472 university students enrolled in statistics courses of Health Sciences majors. A Structural Equation Modeling (SEM) approach showed the attitudes as the stronger direct predictor of performance, and played a full mediating role on the relationship between statistics anxiety and performance. Contrary to hypothesized, the direct contribution of math background, trait anxiety, and test anxiety to performance was non-significant. A final model posited that performance was positively and directly affected by attitudes, and in turn attitudes were positively influenced by math background and negatively affected by anxiety. Math background also appeared as negative predictor of anxiety. Finally, test anxiety was a positively direct predictor of statistics anxiety.Keywords: Attitudes, anxiety, statistics performance, test anxiety, structural equation modeling. ResumenEl estudio investiga las relaciones entre bagaje matemático, ansiedad rasgo, ansiedad ante los exá-menes, ansiedad ante la estadística, actitudes hacia la estadística, y rendimiento, en una muestra de 472 estudiantes de asignaturas estadísticas de Ciencias de la Salud mediante modelos de ecuaciones estructurales. Las actitudes son el principal predictor del rendimiento y mediadoras entre ansiedad y rendimiento. Las relaciones entre bagaje matemático, ansiedad rasgo, y ansiedad ante los exámenes, sobre el rendimiento no fueron significativas, contra hipótesis. El modelo final postula que el rendimiento está afectado directa y positivamente por las actitudes, y éstas son influidas positivamente por el bagaje matemático, y negativamente por la ansiedad. El bagaje matemático es predictor negativo de la ansiedad y la ansiedad ante los exámenes es un predictor directo positivo de la ansiedad ante la estadística.Palabras clave: Actitudes, ansiedad, rendimiento en estadística, ansiedad ante los exámenes, modelos de ecuaciones estructurales.

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