Suchergebnisse

Background: Intuitionistic fuzzy sets (IFS) represent a methodology for quantifying latent variables in questionnaire analysis through membership and non-membership functions, which are linked by an uncertainty function. Objectives: We aim to apply an IFS approach to the problem of students' satisfaction of university teaching. Such framework can take into account a source of uncertainty related to items and another related to subjects. Results: A new technique for IFS analysis is set forth and generalized to a multivariate scenario. Potential advantages of the IFS perspective with respect to other nonfuzzy approaches are provided. Application: We apply this method to a national program of university courses evaluation and we focus, in particular, on the outcomes of two Masters in Statistics.

"Business surveys are a valuable indication of the current and the future economic situation. However refusals are very common in this context and may induce bias in the estimates of interest. In this paper the problem of adjusting for nonresponse estimators of relevant economic outcomes is considered. Using a large simulation study, the authors investigate how weighting adjusted procedures are influenced by the specification of the response model utilized in calculation of the weights. They consider, in particular, how trimming the weights can have an impact on the final estimates and they propose a bootstrap-based procedure to determine an optimal trimming threshold. The authors illustrate the procedure using a 2009 survey of a large population of Italian firms." (author's abstract)

L'opera si propone di illustrare in modo sintetico e sistematico le tecniche di stima dei parametri di una popolazione finita che fanno uso delle informazioni ausiliarie disponibili, al fine di affrontare i problemi che emergono nelle indagini reali. In queste infatti ci si trova a dover fronteggiare gli effetti delle imperfezioni nelle basi di campionamento, della mancata osservazione di tutte le variabili da rilevare o di una parte di esse nelle unità designate a far parte del campione, degli errori di misura. Il volume si propone di rendere il lettore consciodi tali effetti e capace di farv