Modelos estadísticos y evaluación: tres estudios en educación

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 university admission is been discussed. The present paper summarizes part of the research done by the author in her PhD. The context for this thesis is the evaluation of large-scale and complex systems of assessment. The main objectives were: to achieve a deep knowledge of the entire university admissions process in Spain, to discover the main sources of uncertainty and to promote empirical research in a continual improvement of the entire process. Focusing in the suitable statistical models and strategies which allow to high-light the imperfections of the system and reduce them, the paper develops, among other approaches, some applications of multilevel modeling.PAAU exams, admissions process, random coefficient models, variance component models, rater reliability

The role of incidental variables of time in mood assessment

Determining what influences mood is important for theories of emotion and research on subjective well-being. We consider three sets of factors: activities in which people are engaged; individual differences; and incidental variables that capture when mood is measured, e.g., time-of-day. These three factors were investigated simultaneously in a study involving 168 part-time students who each responded 30 times in an experience sampling study conducted over 10 working days. Respondents assessed mood on a simple bipolar scale – from 1 (very negative) to 10 (very positive). Activities had significant effects but, with the possible exception of variability in the expression of mood, no systematic individual differences were detected. Diurnal effects, similar to those already reported in the literature, were found as was an overall “Friday effect.” However, these effects were small. Lastly, the weather had little or no influence. We conclude that simple measures of overall mood are not greatly affected by incidental variables.Affect; mood; experience sampling; diurnal effects; day-of-the-week; weather; multilevel analysis. leex

Unsupervised domain adaptation for bladder segmentation by U-net in Cone Beam CT

The main goal of this project is to accomplish the automatic segmentation of CBCT radiotherapy images using Deep Learning. Why? Because they are used in some process to treat cancer, in order to analyze where the radiation has to be applied. And we think that, by segmenting the images, the treatment applied to the patient could be executed more precisely, so the healthy tissues and organs around the tumor area would be less affected. This project is supervised by Benoît Macq and Eliott Brion, from ICTEAM research group at UCLouvain.Introduction: Radiotherapy is a medical treatment used to control or kill cancerous cells in cancer patients. At the beginning of the treatment planning process, the patient takes a CT scan in order to plan his radiation dose and, sometimes, he can take a Cone Beam CT scan some days after, right before receiving his radiation, to adjust his couch position for the delivery. The main difference between CT and CBCT scans is that the first one has a higher quality and contrast, and the second one is taken directly at the isocenter. As the treatment planning takes several days, when the patient receives his radiation his organs might not be in the same position as they were at the beginning, so the healthy tissues around the tumor area can receive more radiation than what it was planned and get damaged. Our aim is to implement an automatic segmentation of the bladder in CBCT 3D images using deep learning, in order to get a clearer idea of the position of those organs. Materials and Methods: In order to implement the segmentation we performed unsu- pervised domain adaptation between CT (the source) and CBCT 3D images (the target), as we didn?t have a large labeled CBCT dataset but we did for CT, as their segmenta- tion is already part of the treatment planning process. We have used a subset dataset of 120 patients: 60 CT and 60 CBCT of the male pelvic region. We have implemented a deep learning network using Unet as a segmenter and a regular CNN as a domain discriminator (an adversarial network), which also includes a gradient reversal layer. We have used the Dice score coefficient and the Hausdorff distance in order to evaluate the performance of our network and compare it with some previous works developed in the same field. Results: We have performed three main experiments, for which we have obtained the following DSC and Hausdorff distance (in voxels): (i) lower boundary: 0.383±0.260 and 36.47, (ii) upper boundary: 0.717±0.177 and 27.44, (iii) unsupervised domain adapta- tion: 0.623±0.149 and 39.18. With this implementation we have closed the gap between training the network only on CT and only on CBCT by a 72%. Conclusions: Cone Beam CT image segmentation using unsupervised domain adap- tation proves to be an improving methodology in radiotherapy and presents different applications in other fields

University admission marks in Catalonia: Some highlights from the empirical research

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 general emphasis is put upon the concurrent research and empirical evidence about the properties of the examination items and scores. After a discussion about the limitations of the exams' format and appropriateness of the instruments used in the study, the article concludes with some suggestions to improve such examinations.Admissions process, reliability of grading, index of difficulty, discrimination power

Asessing public policies. The case of education in Europe and the interaction between personal and institutional factors

The paper deals with the comparative study of European citizens’ satisfaction with the state of education in their respective countries. Individual and contextual effects are tested applying multilevel analysis. The results show that educational public policies (level of decentralization, degree of comprehensiveness and public spending) as well as the students’ social environment (socioeconomic and cultural status) have a sound impact on the opinions about the state of education.Education, public opinion, public policies, multilevel analysis, comparative studies, European Social Survey

Improving social measurements: The experience of the ESS first rounds in Spain

With the two aims of monitoring social change and improving social measurement, the European Social Survey is now closing its third round. This paper shows how the accumulated experience of the two first rounds has been used to validate the questionnaire, better adapt the sampling design to the country characteristics and efficiently commit fieldwork in Spain. For example, the dynamic character of the population nowadays makes necessary to estimated design effects at each round from the data of the previous round. The paper also demonstrates how, starting with a response rate of 52% at first round, a 66% response rate is achieved at the third round thanks to an extensive quality control conducted by the polling agency and the ESS national team and based on a detailed analysis of the non-response cases and the incidences reported by the interviewed in the contact form.European social survey, fieldwork, response rate, sampling design

The European Social Survey. Methodological aspects

From a scientific point of view, surveys are undoubtedly a valuable tool for the knowledge of the social and political reality. They are widely used in the social sciences research. However, the researcher's task is often disturbed by a series of deficiencies related to some technical aspects that make difficult both the inference and the comparison. The main aim of the present paper is to report and justify the European Social Survey's technical specifications addressed to avoid and/or minimize such deficiencies. The article also gives a characterization of the non-respondents in Spain obtained from the analysis of the 2002 fieldwork data file.European Social Survey, comparative studies, fieldwork, non-respondents

Associationism and electoral participation: A multilevel study of 2000 Spanish general election

This work presents an application of the multilevel analysis techniques to the study of the abstention in the 2000 Spanish general election. The interest of the study is both, substantive and methodological. From the substantive point of view the article intends to explain the causes of abstention and analyze the impact of associationism on it. From the methodological point of view it is intended to analyze the interaction between individual and context with a modelisation that takes into account the hierarchical structure of data. The multilevel study of this paper validates the one level results obtained in previous analysis of the abstention and shows that only a fraction of the differences in abstention are explained by the individual characteristics of the electors. Another important fraction of these differences is due to the political and social characteristics of the context. Relating to associationism, the data suggest that individual participation in associations decrease the probability of abstention. However, better indicators are needed in order to catch more properly the effect of associationism in electoral behaviour.Electoral abstention in Spain, multilevel modelling

Monitoring the university admissions process in Spain

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), maintenance of standards, and compilation and use of the grading process, and their integration in the operational grading are proposed. Various schemes for score adjustment are reviewed and feasibility of their implementation discussed. The advantages of pretesting of items and of empirical checks of experts' judgements are pointed out. The paper concludes with an outline of a planned reorganisation of the higher education in Spain, and with a call for a comprehensive programme of empirical research concurrent with the operation of the examination and scoring system.Admissions process, examinee's choice, pretesting, rater reliability, score adjustment

Algunos factores que inciden en el rendimiento y en la evaluación de los alumnos en las PAAU

The context where the university admissions exams are performed is presented and the main concerns about this exams are outlined and discussed from a statistical point of view. The paper offers an illustration of the use of random coefficient models in the study of educational data. The association between two individual scores (one internal and the other external to the school) and the effect of the school in the external exam is analized by a regression model with random intercept and fixed slope. A variance component model for the analysis of the grading process is also presented. The paper ends with an outline of the main findings and the presentation of some specific proposals to improve and control the equity of the system. Some pedagogic reflections are also included.PAAU exams, COU' scores, admisssions process, random coefficient models, variance component models, rater reliability