Comment mobiliser les ressources des acteurs afin de favoriser une prise en charge plus rapide et plus adéquate des mineurs en situation d’absentéisme ou de décrochage scolaire ? Vers un référentiel commun.

Comment mobiliser les ressources des acteurs afin de favoriser une prise en charge plus rapide et plus adéquate des mineurs en situation d’absentéisme ou de décrochage scolaire ? Vers un référentiel commun

Spectral Quality of University Standardized Tests - Development of edumetrical indices for the analysis of the spectral quality of higher education standardized tests and application to the MOHICAN check up ’99 tests

For several decades almost all European university institutions have been faced with a strong increase in their number of students whereas the allocated budgets have not increased in proportion (Gibbs & Jenkins, 1992). The universities of the French Community of Belgium do not escape this heavy tendency: compared with the 1972 situation, the number of students has increased to 150% and, in constant francs, subsidies have remained unchanged (Debry & al., 1998). This situation leads in the first cycles of studies, where the students are most numerous, to a massive use of standardized examinations with multiple choice questions (MCQ) which makes the assessment of great groups of students possible within reasonable time delays. The confidence degrees technique associated to the MCQ makes it possible to bypass the "binary" character of students assessment performance (the selected proposal is either correct, or incorrect) provided that a series of methodological rules are followed called "admissible probability measurement procedures" by Shufford & al. (1966). Among those rules: ask the students to express their confidence in a numerical (probabilistic) scale. The one adopted offers 6 degrees of subtlety: 0%, 20%, 40%, 60%, 80% and 100% of confidence. By inviting the student to accompany his choice by the percentage of chances to be correct he attributes to his answer, we allow more subtleties in the analysis of his performances. At one extreme, the choice of a wrong answer accompanied by the maximal percentage of certainty (100%) presents the worst situation, in which the student provides an erroneous answer by estimating that he has a maximal chances to be correct. On the other hand, the student who answers correctly with a maximal certainty shows an assured performance. Between these two extremes, other zones can be identified in the "spectral analysis" of the performances. Jans & Leclercq (1999) propose a specific terminology. They distinguish "ignorance" (correct answer and weak certainty), from "partial knowledge" (correct answer and average certainty), and "perfect knowledge" (correct answer and high certainty). Such spectral gradations were also considered by these authors in the case of an incorrect answer ("mistaken knowledge" and " fallacious knowledge" or "dangerous knowledge"). Usually, the confidence percentages which accompany the MCQ answers are used to deliver more subtler feedback on each student's spectral performances. The innovative aspect of our approach lies in the fact that we have exploited the confidence percentages provided by the students to provide spectral information on the quality of the questions (as opposed to information on the quality of students performances). Our research thus led to the development of a series of original indices for the analysis of assessments' spectral quality. These spectral indices are intended to be used when the assessor must highlight problematic MCQ and, within those, the proposals which contain anomalies. Our starting intuition for the construction of these new indices is as follows: logically the students who answer a question correctly should provide percentages of certainty higher than the students who answer incorrectly. Thus, for a multiple choice question which functions normally from the point of view of the certainty percentages use, we should observe among the students who choose the correct answer a tendency to answer with higher percentages of certainty and, in parallel, among the students who choose a wrong proposal a tendency to answer with lower percentages of certainty. We will then say that there is "spectral coherence". In the case where this situation does not arise, for example when students choose higher certainty percentages for one of the incorrect answers rather than for the correct answer, we are confronted with a problem of inconsistency in the use of the percentages of certainty, we will then speak of "spectral inconsistency". To measure spectral coherence we created two new types of indices starting from the classical point bi serial correlation coefficient (classical rpbis) calculation principle. Let us recall that in the case of the rpbis, the choices or the rejections (1 or 0) of each proposal of a MCQ are correlated with the numbers of correct answers obtained to the whole test. The classical rpbis makes it possible to evaluate up to what extent each proposed alternatives solutions of each MCQ discriminates the students according to the criterion of the number of correct answers. Logically, one expects that the students who collect a high number of correct answers tend to choose the correct answer for a given question and that the students which collect a lower number have a tendency to choose an incorrect proposal. The two new types of spectral coherence indices of measurement are: (1) the Spectral Contrasted rpbis (rpbis SC) and (2) the Spectral Contrasted rpbis calculated after Turbo analysis (rpbis SCT). During a former research we had already used information related to the confidence degrees to calculate a new type of rpbis, the Spectral rpbis or rpbis S (Gilles, 1998). The rpbis S was developed in order to analyze the tendency to use higher certainty in case of correct answers than in case of incorrect answers. Within the framework of this thesis we propose a first improvement of the rpbis S by implementing a "contrasted treatment" for the MCQ incorrect proposals. We use the name "rpbis SC" to indicate the rpbis S is constructed with a "Contrasted treatment" which consists in the computation of the rpbis SC of an incorrect answer by using the data of the students who choose this wrong response in contrast with the data restricted to the students who choose the correct answer excluding the data from the students who choose an other incorrect answer. The advantage lies in the elimination of the data of the students who have chosen the other incorrect answers. This avoids introducing into the measurement of spectral coherence, the "background noise" generated by the data of the other incorrect answers. The principle of "turbo analysis", consists in operating a selection in the data used for rpbis SC calculation on the basis of the level of realism reached by the students. We can thus increase the reliability of information related to the spectral indices by restricting the data to the students who make less errors in their self-assessments (in their use of certainty percentages). We measure the level of errors of self-assessments made by the students by using the index of realism which varies from 0 to 100 (Leclercq & al, 2000). The name rpbis SCT indicates rpbis SC calculated with a Turbo analysis. The word "turbo" refers to the rise to power of the instrument in terms of the quality of information provided as one restricts oneself progressively to data from sets of students who make less and less errors in their self-assessments. We mention in the index's name the threshold of realism used to select the data. For instance rpbis SCT80 was calculated starting from the data of the students whose realism is equal to or higher than 80 (those who make between 0% and 20% of errors in their self-assessments). The new indices rpbis SC and rpbis SCT, which are in the heart of this research, are designed for the detection of problems located at the "alternatives level" inside the MCQ. We also adapted other spectral indices initially planned for the analysis of students performances so that these indices deliver information on the MCQ performances, at a "question level". On one hand, the index of Realization of the predictions by question (Rq) or the quantity of errors of self-assessment contained in the results for a question and, on the other hand, the index of Centration per question (Cq) or the level of over or under confidence in the results for a question. Lastly, we also measured the level of spectral coherence of a question (NCSq) by taking into account the rpbis SC of the various proposals of a MCQ. The "turbo analysis" principle was also applied to the calculation of these spectral indices. We tried to test these new spectral indices designed for detection of suspect alternatives within suspect MCQ using the data of several thousands of answers and certainty percentages collected during the ten standardized tests of the MOHICAN project (Leclercq & al., 2001). They consisted in ten tests of knowledge of the principal subjects at the level of the end of secondary education which were submitted to groups of students entering first year studies in eight of the nine university institutions of the French Community of Belgium (the number of questioned students varied between 1.392 and 3.846 according to tests). These standardized tests consisted of MCQ for which students were invited to choose one answer and systematically accompany it with a percentage of certainty. The students had, not only to state which was their correct proposal, but also which was the percentage of chances to be correct that they granted to each one of their answers. No academic scores were delivered for these (Check up) MOHICAN tests (each student received a diagnostic feedback and the assessors a global feedback). Anonymity was guaranteed. The choice of the percentages of certainty was thus influenced neither by a scale of tariff of points nor by granting a final score which could have affected the later academic course of the student. The total number of MCQ for the ten MOHICAN tests was 173. For two MCQ among them, the 3rd and the 20th question of the general knowledge test in History and Socio-Economy, the values obtained with the spectral rpbis indicate situations of marked spectral inconsistency, the students tending to give lower percentages of certainty for the answers considered as correct and higher percentages of certainty for the incorrect answers. Studying the proposals of the two problematic MCQ by using the classical rpbis indices, we notice that the two MCQ do not function correctly from the point of view of classical discrimination. When we ask for the opinion of the experts of the contents, they confirm that the two MCQ display problematic results: for one of the questions a wrong proposal could also be regarded as being a correct answer and for the other, there is an error in the encoding of the correct answer. For these two questions there is thus convergence of three different perspectives: (1) that of the classical rpbis, (2) that of the experts and, (3) that of the spectral coherence measured using the spectral rpbis. In the case of the MOHICAN tests, the spectral analysis thus allows to highlight two questions that a more qualitative analysis (posterior opinions of the experts) as well as a classical analysis of discrimination (classical rpbis) also indicate as questions with problems. Does the spectral analysis make it possible to perform better than the classical analysis of discrimination (classical rpbis) for locating the problematic questions and the proposals which contain anomalies? This issue has been tested. We analyzed the 173 MCQ of the 10 MOHICAN tests by using the spectral rpbis (rpbis SC, rpbis SCT80 and rpbis SCT90) as well as the classical rpbis indices. We also reviewed the comments formulated by the experts of the contents in connection with each question. From these analyses it comes out that in addition to the two MCQ already discovered previously, 14 other questions are highlighted. The classical rpbis indicates anomalies in each one of these 14 MCQ. Six MCQ present abnormal values at rpbis SC. Only one MCQ obtains an abnormal rpbis SCT80. No MCQ obtains an abnormal rpbis SCT90. Among these 14 questions, only 3 are pointed as problematic by the experts. With regard to the three questions singled out by the experts, they lead to a set of proposals that only the rpbis SC designates, whereas for the rpbis SCT80 and the rpbis SCT90, they are not highlighted. As far as the classical rpbis is concerned one only of the two problematic proposals for only one of the three questions appears. Therefore, from the point of view of "detection", rpbis SC were more effective to highlight the problems raised by the experts than were the other indices. This analysis shows that the various types of rpbis induce also "false alarms", abnormal values collected by proposals whereas the experts of the contents do not detect particular problems. From this point of view, the rpbis SC, with 7 false alarms, is less effective than the rpbis SCT80 which causes only one of them and less than the rpbis SCT90 which starts none, but rpbis SCT80 and rpbis SCT90 fail by "undetecting" the three questions pointed by the experts. On the other hand the rpbis SC starts less false alarms than the classical rpbis which has 10 false alarms. These qualities of lower "undetection" and less "false alarms" are crucial when the question arises of highlighting a problematic MCQ. When we correct the anomalies contained in certain answers within the MCQ, we can, from now on, not only evaluate the spectral impact of these corrections on the answers ("alternatives level"), but also on the whole question by comparing the values obtained with the indices of NCSq, Rq and Cq before and after changes are operated (at the "question level"). We did this for the two most problematic questions of the general knowledge test in History and Socio Economy and quantified the gains in spectral coherence. The improvement of the spectral coherence of the test was also measured by calculating the average values of the spectral indices at the "question level". These average indices thus made it possible to evaluate the spectral impact on a third "test level" of the assessment. In parallel, we also observed an improvement of the fidelity of the test using the classical Cronbach's alpha coefficient. Using the spectral indices developed within the framework of our thesis and usable with three levels of spectral analysis: "ALTERNATIVES", "MCQ" and "TEST", we open a new way for the analysis of the quality of standardized tests and their regulation. We are now able to evaluate the spectral quality of higher education standardized tests using confidence degrees, to highlight possible anomalies in the questions; and, after corrections, to evaluate the spectral impact of the improvements. This is the main contribution of our thesis to the improvement of procedures that control the quality of standardized tests and, by extension, to the improvement of the reliability of the students scores, which, in fine, constitutes the stake of our edumetric concerns.Depuis plusieurs décennies la plupart des institutions universitaires européennes sont confrontées à une forte augmentation de leurs effectifs d'étudiants alors que les budgets alloués n'augmentent pas en proportion (Gibbs & Jenkins, 1992). Les universités de la Communauté Française de Belgique n'échappent pas à cette tendance lourde : par rapport aux chiffres de 1972, le nombre d'inscrits est passé à 150% et, en francs constants, les subsides sont restés les mêmes (Debry & al., 1998). Cette situation entraîne dans les sections des premiers cycles d'études où les étudiants sont les plus nombreux, un recours massif aux examens standardisés avec questions à choix multiple (QCM) ce qui permet d'évaluer dans des délais raisonnables de grands groupes d'étudiants. La technique des degrés de certitude associée aux QCM permet de dépasser le caractère " binaire " de l'évaluation des performances des étudiants (la proposition choisie est soit correcte, soit incorrecte) à condition de veiller à respecter une série de règles méthodologiques que Shufford & al. (1966) appellent " admissible probability measurement procedures ". En invitant l'étudiant à accompagner son choix d'une proposition du pourcentage de chances qu'il lui attribue d'être correcte, nous permettons plus de nuances dans l'analyse de ses performances. A un extrême, le choix d'un distracteur accompagné du pourcentage de certitude maximum (100%) présente la pire des situations, celle où l'étudiant fournit une réponse erronée en estimant qu'elle a un maximum de chances d'être correcte. A l'opposé, l'étudiant qui répond correctement avec une certitude maximale fait preuve d'une connaissance assurée. Entre ces deux extrêmes, s'ouvre tout l'espace d'une analyse " spectrale " (et non plus " binaire ") des performances, espace invisible lorsque les pourcentages de certitude ne sont pas utilisés. Ainsi, dans le cas d'une réponse correcte, Jans & Leclercq (1999) proposent une terminologie ad hoc pour distinguer une " ignorance " (réponse correcte et certitude faible), d'une " connaissance partielle " (réponse correcte et certitude moyenne), d'une " connaissance parfaite " (réponse correcte et certitude élevée). De telles nuances spectrales ont aussi été envisagées par ces auteurs dans le cas d'une réponse incorrecte (" méprise " et " connaissance dangereuse "). Habituellement les pourcentages de certitude qui accompagnent les réponses aux QCM sont utilisés pour livrer des informations nuancées, spectrales (et non plus binaires), sur la qualité des performances des étudiants. L'aspect novateur de notre démarche réside dans le fait que nous avons exploité les certitudes fournies par les étudiants pour livrer cette fois des informations spectrales sur la qualité des questions (différentes des informations sur la qualité des performances des étudiants). Notre recherche a ainsi débouché sur l'élaboration d'une série d'indices originaux d'analyse de la qualité spectrale des épreuves. Ces indices spectraux sont destinés à être utilisés lors de la phase de correction d'une évaluation, lorsqu'il s'agit de mettre en évidence les QCM problématiques et, au sein de celles-ci, les propositions qui contiennent des anomalies. Notre intuition de départ pour la construction de ces nouveaux indices est la suivante : logiquement les étudiants qui répondent correctement à une question devraient fournir des pourcentages de certitude plus élevés que les étudiants qui répondent incorrectement. Ainsi, pour une question à choix multiple qui fonctionne normalement du point de vue de l'utilisation des certitudes, nous devrions observer chez les sujets qui ont choisi la proposition correcte une tendance à fournir des pourcentages de certitudes en moyenne plus élevés que les pourcentages de certitude utilisés par les sujets qui se sont trompés. Parallèlement, pour chacune des propositions incorrectes, nous devrions aussi observer une tendance à choisir des pourcentages de certitude moins élevés que les pourcentages de certitude qui ont accompagné la réponse correcte. Nous dirons alors qu'il y a " cohérence spectrale ". Dès lors que cette situation ne se présente pas, par exemple lorsque les sujets ont tendance à fournir des certitudes plus élevées pour une des propositions incorrectes que pour la réponse correcte, nous nous trouvons face à un problème d'incohérence dans l'utilisation des pourcentages de certitude, nous parlerons alors " d'incohérence spectrale ". Pour mesurer la cohérence spectrale nous avons créé deux nouveaux types d'indices au départ du principe de calcul du rpbis classique. Rappelons que dans le cas du rpbis classique, les choix ou les rejets (1 ou 0) de chaque proposition d'une QCM sont corrélés avec les nombres de réponses correctes obtenues à l'ensemble des questions du test. Le rpbis classique permet d'évaluer dans quelle mesure la question discrimine les étudiants en fonction du critère du nombre de réponses correctes. Logiquement, on s'attend à ce que les sujets qui récoltent un nombre élevé de réponses correctes aient tendance à choisir la proposition correcte et les sujets qui récoltent un nombre moins élevé aient eux tendance à choisir une proposition incorrecte. Les deux nouveaux types d'indices de mesure de la cohérence spectrale sont : (1) le rpbis Spectral Contrasté (rpbis SC) et (2) le rpbis Spectral Contrasté calculé après Turbo analyse (rpbis SCT). Lors d'une recherche antérieure nous avions déjà utilisé les informations liées aux degrés de certitude pour calculer un nouveau type de coefficient de corrélation de point bisériale, le rpbis spectral ou rpbis S (Gilles, 1998). Le rpbis S a été développé en vue d'analyser la tendance à utiliser des certitudes plus élevées dans le cas d'une réponse correcte que dans le cas des réponses incorrectes. Dans le cadre de cette thèse nous proposons une première amélioration du rpbis S en mettant en œuvre un " traitement contrasté " pour les propositions incorrectes des QCM. Nous utilisons l'appellation rpbis SC pour désigner les rpbis S qui bénéficient du " traitement Contrasté " qui consiste à faire intervenir dans le calcul du rpbis SC d'une proposition incorrecte les données des étudiants qui ont choisi cette proposition en contraste avec les seules données des étudiants qui ont choisi la proposition correcte. L'avantage réside dans l'élimination des données des étudiants ayant opté pour les autres propositions incorrectes, ce qui évite d'introduire dans la mesure de la cohérence spectrale du distracteur envisagé, le " bruit " qu'engendreraient les données des autres propositions incorrectes. En ce qui concerne le principe de la " turbo analyse " il s'agit d'opérer une sélection dans les données utilisées pour le calcul des rpbis SC sur la base du critère du niveau de réalisme atteint par les sujets. Nous pouvons ainsi accroître la confiance dans les informations liées aux indices spectraux en ne prenant en compte que les données des étudiants qui commettent le moins d'erreurs dans leurs auto-estimations. Nous mesurons la quantité d'erreurs d'auto-estimations commises par les sujet

Hydrological behaviour of the granitic Strengbach catchment (Vosges massif, Eastern France) during a flood event

A field campaign combining monitoring devices and determination of isotopes and chemical elements has been performed during a summer thunderstorm in the small granitic Strengbach catchment (Vosges, France). The collected ground data were used in a hydrological modelling exercise including two conceptual rainfallrunoff models (GR4, TOPMODEL). The predominant role in flood generation of pre-event water coming from the superficial layers of the water saturated area has been shown and a conceptual scheme has been proposed derived from the field observations. The two tested modelling structures and assumptions are not able to take into account fully the complexity of the physical processes involved in flood generation

Sources and sinks of sediment-bound contaminants in the Gulf of Lions (NW Mediterranean Sea): A multi-tracer approach

Surficial sediments collected in 2002 throughout the Gulf of Lions continental shelf (NW Mediterranean) were analysed for trace metals (Cd, Co, Cr, Cs, Cu, Ni, Pb, Sr, Zn and Zr), major elements (Al, Ca, Fe, P and Ti) and the sewage marker coprostanol. In addition, particle size distribution, organic carbon (OC) and carbonates were also determined. Results showed that the metal contamination (Cd, P, Cu, Pb and Zn) is mainly introduced by the local rivers and accumulates—via a regulation by OC and silt fraction (2–63 mm)—in the direct vicinity of the mouths, in high shear stress environments. Here also the signal of sewage contamination is the best preserved, especially off the eastern point sources where local sedimentation rates save the faecal marker from biodegradation processes. It is demonstrated that the shallow prodeltas are the first repository areas for land-derived particles, exposing local ecosystems to both inorganic and organic contaminations. When going seaward, however, sediment dilution, particle sorting and biodegradation processes make that most riverborne contaminants rapidly reach natural levels. Only some metals (i.e. Pb and Zn)—closely associated with the clay fraction—still depict anthropogenic enrichment, which seems to be inherited from man-made aerosols

Génération et placement de couleurs sur une vue de type métro

International audienceThe schematic views for metro maps are used to maximize the transmision of relevant information (lines, metro stops) of network visualization. Automatic generation of metro maps focus primarily on the physical structure of the network, but little on the choice of colors which is an accurate visual discrimination. In this article, we propose to invesigate the generation and placement of colors to be assigned to lines of a network. The first step is to find as many colors as lines of the network. These colors must be perceptually as distant as possible, and available in the vocabulary of colors. The second step is to place these colors so that the closest lines have the more distant color. The positioning of colors is a NP-complete problem, thus we use a meta-heuristic approach to solve it. To validate our method, we apply it to the field of air traffic control with the maps of Flight Routes

Conception instrumentée du rendu graphique des interfaces

International audienceWe propose to define the activity of graphical rendering design, which aims at maximizing the display quality of the image components. Overlooked in most design methods, this activity is essential for the success of a design project and for the validation of interfaces of critical systems. As such, it is pluri-disciplinary: graphical design (design, infovis), evaluation (experimental psychology), influence from hardware and software technologies (computer science), design methodology (design rationale, maintenance, computer science). In this paper, we detail the activity of graphical rendering design of HMI, by identifying its main dimensions. We also present a tool that instruments it: we describe its main functionalities, as well as the methods allowing to achieve the activity. Finally, we discuss about the benefits of inter disciplinary instrumentation during the design process

Effets des paramètres graphiques sur la perception visuelle : experimentations sur la forme, la surface, l'orientation des objets et la définition des écrans

International audienceUser interfaces of critical systems, such as air traffic control displays, use graphical objects to code for an ever increasing amount of information. This evolution brings forth concerns about the detection and identification of the displayed objects, in particular for small size objects. First, graphic properties of the interface should include some knowledge about the interplay between colour, shape and size interactions, and the visual perception. Second, the redesign of any interactive system should take into account the particularities of the evolving software and hardware display technology (pixel size and structure, for example) in order to preserve crucial aspects of the initial visual display. The two experiments described in this paper are aiming towards building a more systematic knowledge of graphic properties interactions per se, and their changes as a function of display technologies. More precisely, we examined the effect of the object size, shape and luminosity, as well as its contrast with the background. Results show that object perception is dependent upon its size, its contrast with the background and the overall luminosity of the background. Furthermore, for small size objects, interactions between pixel luminosities and pixel arrangement greatly influence their perception by the human eye