Influence de la question dans une epreuve relative a la notion d'independance

Resume Ce travail est une contribution à l'étude des acquisitions spontanées des élèves en ce qui concerne la notion d'indépendance en probabilités. Une de nos hypothèses générales est que, dans le champ des phénomènes aléatoires, de légères modifications de la présentation d'un problème sont susceptibles d'avoir une influence nette sur les conduites des élèves. Cette hypothèse semble fondée: en effet, les performances à l'épreuve ici retenue-bien que toujours favorables-sont très sensibles à la forme de la question posée dans l'énoncé. Nous essayons d'interpréter ce résultat en analysant les modifications de la tâche impliquées par le changement de forme de la question et en examinant les arguments exprimés par les éléves.

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Influence of the question in a task on the concept of independence

This work is a contribution to the study of spontaneous assimilation by students concerning the concept of independence in probability. One of our general hypotheses is: in the field of random phenomena, slight modifications of the presentation of a problem are likely to have a distinct influence on students behaviour. This hypothesis seems justified: indeed, performances of the task designated here, although always relatively successful, are very sensitive to the form of the question given in the problem. We try to interpret this result by analysing the modifications of the task implied by the change of form in the question, and by examining the arguments expressed by the students.

     

On the compression of search trees

Let X=_x1,_x2,…,_xn$X=x_1\text{,}{x}_2\text{,}\dots \text{,}{x}_n$ be a sequence of non-decreasing integer values. Storing a compressed representation of X that supports access and search is a problem that occurs in many domains. The most common solution to this problem uses a linear list and encodes the differences between consecutive values with encodings that favor small numbers. This solution includes additional information (i.e. samples) to support efficient searching on the encoded values. We introduce a completely different alternative that achieves compression by encoding the differences in a search tree. Our proposal has many applications, such as the representation of posting lists, geographic data, sparse bitmaps, and compressed suffix arrays, to name just a few. The structure is practical and we provide an experimental evaluation to show that it is competitive with the existing techniques.     

Personality profiles and dogmatism in undergraduate teacher education students

A sample of 435 junior education majors in a large Southwestern university were given the 16 Personality Factor Questionnaire and the Opinion Scale. Correlations were computed between these two scales, and a profile of personality factors was developed which defined the nature of authoritarianism or dogmatism. A step-wise multiple regression analysis revealed that an accurate prediction formula for dogmatism could not be developed from the personality factor scores. Implications for teacher education programs include research to determine if treatment programs can be developed to change a student's degree of dogmatism, and the importance of screening procedures which include an assessment of open-mindedness.     

Plant breeding in vitro

Over the centuries a variety of techniques have been developed to propagate plants vegetatively — dividing, layering, and grafting. These traditional methods are all slow, however, and in recent years there has been much interest in ‘test-tube’ breeding of plants. This is not only very fast — a single rose can produce up to 400 000 descendants in a single year — but is also a very valuable means of eradicating plant diseases.     

The persistence of social attraction in socially deprived and satiated rats

Pairs of socially deprived or satiated rats were observed for 71÷2 continuous hours in an open field. Social contact increased monotonically throughout this time, with socially deprived animals showing more attraction, and a greater increase in attraction, than satiated animals. The quality of social contact changed, however, from a predominantly active interaction, in which the most sociable animals were most mobile, to a predominantly passive huddling, in which the most sociable animals were least mobile. The results suggest that social attraction in rats is not transitory, and may serve several different functions.