That individuals contribute in social dilemma interactions even when contributing is costly is a well-established observation in the experimental literature. Since a contributor is always strictly worse off than a non-contributor the question is raised if an intrinsic motivation to contribute...

The examinations taken by high-school graduates in Spain and the role of the examination in the university admissions process are described. The following issues arising in the assessment of the process are discussed: reliability of grading, comparability of the grades and scores(equating),...

The educational system in Spain is undergoing a reorganization. At present, high-school graduates who want to enroll at a public university must take a set of examinations Pruebas de Aptitud para el Acceso a la Universidad (PAAU). A "new formula" (components, weights, type of exam,...) for...

In 2007 the first Quality Enhancement Meeting on sampling in the European Social Survey (ESS) took place. The discussion focused on design effects and inteviewer effects in face-to-face interviews. Following the recomendations of this meeting the Spanish ESS team studied the impact of...

The results of the examinations taken by graduated high school students who want to enrol at a Catalan university are here studied. To do so, the authors address several issues related to the equity of the system: reliability of grading, difficulty and discrimination power of the exams. The...

We construct a weighted Euclidean distance that approximates any distance or dissimilarity measure between individuals that is based on a rectangular cases-by-variables data matrix. In contrast to regular multidimensional scaling methods for dissimilarity data, the method leads to biplots of...

Canonical correspondence analysis and redundancy analysis are two methods of constrained ordination regularly used in the analysis of ecological data when several response variables (for example, species abundances) are related linearly to several explanatory variables (for example,...

The problem of outliers is well-known in statistics: an outlier is a value that is far from the general distribution of the other observed values, and can often perturb the results of a statistical analysis. Various procedures exist for identifying outliers, in case they need to receive special...

Most methods of multivariate analysis rely on a measure of proximity between individual cases or samples to quantify inter-sample differences. The choice of this measure is fundamental to the method and its subsequent results. For example, when data are abundance counts of a set of species at...

Correspondence analysis, when used to visualize relationships in a table of counts (for example, abundance data in ecology), has been frequently criticized as being too sensitive to objects (for example, species) that occur with very low frequency or in very few samples. In this statistical...