Collaborateurs de la Faculté des sciences

2015-7-15, Guinand, Mihaela Catalina, Tillé, Yves

2015-12-12, Guinand, Mihaela Catalina, Tillé, Yves

2014-7-9, Guinand, Mihaela Catalina, Tillé, Yves

2018-4-10, Knauer, Anina C, Bakhtiari, Mojtaba, Schiestl, Florian P

The puzzling diversity of flowers is primarily shaped by selection and evolutionary change caused by the plant’s interaction with animals. The contribution of individual animal species to net selection, however, may vary depending on the network of interacting organisms. Here we document that in the buckler mustard, Biscutella laevigata, the crab spider Thomisus onustus reduces bee visits to flowers but also benefits plants by feeding on florivores. Uninfested plants experience a trade-off between pollinator and spider attraction as both bees and crab spiders are attracted by the floral volatile β-ocimene. This trade-off is reduced by the induced emission of β-ocimene after florivore infestation, which is stronger in plant populations where crab spiders are present than where they are absent, suggesting that plants are locally adapted to the presence of crab spiders. Our study demonstrates the context-dependence of selection and shows how crab spiders impact on floral evolution.

2016-6-13, Guinand, Mihaela Catalina, Tillé, Yves

2016-10, Guinand, Mihaela Catalina, Tillé, Yves

En Suisse, la discrimination salariale à l'encontre des femmes existe encore, même si elle est interdite par la loi. Plusieurs méthodes ont été proposées pour mesurer les niveaux de discrimination. Trois méthodes sont discutées, dont deux sont déjà bien établies dans la littérature : la méthode de Blinder et Oaxaca et celle de DiNardo, Fortin et Lemieux. La méthode de Blinder et Oaxaca fut la première à être proposée. Plusieurs autres techniques ont ensuite été suggérées. Ces méthodes consistent à établir un modèle entre les salaires et les caractéristiques des salariés comme l'âge, l'ancienneté ou le niveau de formation. La méthode de Blinder et Oaxaca permet de mesurer la discrimination salariale en décomposant les différences entre les salaires moyens en une partie explicable par les caractéristiques des individus et une partie non explicable due à la discrimination. La méthode de DiNardo, Fortin et Lemieux est basée sur une technique de repondération des caractéristiques d'un groupe afin de les rendre identiques à ceux de l'autre groupe. Avec cette méthode, on peut mesurer la discrimination non seulement pour d'autres paramètres comme des quantiles. Cependant, cette méthode ne réussit pas à rendre les distributions des caractéristiques identiques. La troisième méthode que nous proposons est basée sur une approche par calage. Cette approche résout les problèmes rencontrés par les deux premières méthodes. En utilisant le calage, on s'assure que les distributions des caractéristiques sont identiques et on parvient aussi à estimer la discrimination salariale non seulement pour des moyennes, mais aussi pour des quantiles.

2017-9-19, Guinand, Mihaela Catalina, Tillé, Yves

Wage differences between women and men can be divided into an explained part and an unexplained part. The former encompasses differences in the observable characteristics of the members of groups, such as age, education or work experience. The latter includes the part of the difference that is not attributable to objective factors and represents an estimation of the discrimination level. We discuss the original method of Blinder (J Hum Resour 8(4):436–455, 1973) and Oaxaca (Int Econ Rev 14(3):693–709, 1973), the reweighting technique of DiNardo et al. (Econometrica 64(5):1001–1044, 1996) and our approach based on calibration. Using a Swiss dataset from 2012, we compare the estimated explained and unexplained parts of the difference in average wages in the private and public sectors obtained with the three methods. We show that for the private sector, all three methods yield similar results. For the public sector, the reweighting technique estimates a lower value of the unexplained part than the other two methods. The calibration approach and the reweighting technique allow us to estimate the explained and unexplained parts of the wage differences at points other than the mean. By using this, in this paper, the assumption that wages are more equitable in the public sector is analysed. Wage differences at different quantiles in both sectors are examined. We show that in the public sector, discrimination occurs quite uniformly both in lower and in higher-paying jobs. On the other hand, in the private sector, discrimination is greater in lower-paying jobs than in higher-paying jobs.queryPlease check and confirm the given name and family name is correctly identified for the first author and amend if necessary.

2016-4-7, Guinand, Mihaela Catalina, Tillé, Yves

2015-6-4, Guinand, Mihaela Catalina, Vallée, Audrey-Anne

We introduce some basic concepts in survey sampling, defining the common terminology in the field. We touch upon various notions, ranging from the sample selection to questionnaire design and data collection and dissemination. In the first part, special attention is paid to different estimators of some parameters of interest, whereas in the second, they are applied in a technique called “calibration”, whose purpose is to improve the accuracy of the estimations.

2018-8-3, Bakhtiari, Mojtaba, Glauser, Gaëtan, Rasmann, Sergio