1,721,132 research outputs found
A critical review and a comparative study on conditional permutation tests for two-way ANOVA
No full textTwo-way ANOVA methodology is surely one of the most important models in the framework of the experimental design theory, as suggested by the great number of proposed solutions given in literature. Among these, some solutions are nonparametric and particularly, thanks to the availability of modern powerful computing equipments, those based on conditional on observations permutation test have gained great interest. The aim of this work is to present and compare such proposals and to illustrate their possible advantages and disadvantages when applied to some real data-sets
Una proposta di approccio integrato alla Conjoint Analysis
No full textNegli ultimi anni la metodologia della Conjoint Analysis si è rivelata essere uno strumento assai utile nelle studio delle preferenze dei consumatori ed in particolare molto efficace come tecnica statistica di supporto allo sviluppo dei nuovi prodotti. Tuttavia la Conjoint Analysis è tuttora una metodologia che presenta alcuni elementi di criticità tra i quali la definizione di una appropriata sintesi dei risultati alla luce anche del problema della definizione di opportuni segmenti di mercato. In questo lavoro si propone un approccio integrato alla Conjoint Analysis che consiste in una procedura a due passi dove nella prima fase si sottopongono i valutatori ad un esperimento full profile che consideri le caratteristiche più generali del prodotto mentre nella seconda fase si somministra un questionario basato su uno schema adaptive che consente di descrivere più dettagliatamente il prodotto esplicitandone le caratteristiche più specifiche. L’approccio proposto consente da un lato di caratterizzare segmenti omogenei di clientela, dall’altro di stimare per ciascun segmento il prodotto significativamente ottimale
Multivariate and multistrata nonparametric tests: the nonparametric combination method
Full text linkResearchers and practitioners in many scientific disciplines and industrial fields are often faced with complex problems when dealing with comparisons between two or more groups using classical parametric methods. The data arising from real problems rarely are in agreement with stringent parametric assumptions. The NonParametric Combination (NPC) methodology frees the researcher from stringent assumptions of parametric methods and allows a more flexible analysis, both in terms of specification of multivariate hypotheses and in terms of the nature of the variables involved in the analysis. An outline of NPC methodology is given, along with case studies
Improving power of multivariate combination-based permutation tests
No full textDeveloping powerful hypothesis testing procedures
devoted at comparing multivariate populations is quite
a common and relevant topic either from the methodological
and the practical point of view and in this connection the
NonParametric Combination (NPC) permutation methodology
provides a more flexible and effective background for
many multivariate testing problems (Pesarin and Salmaso in
Permutation tests for complex data: theory, applications and
software, 2010a). The goal of this paper is to propose some
specific procedures aimed at possibly improving power of
NPC Tests in the context of the additive linear model. It will
be shown by an extensive simulation study, the improvedin-
power NPC Tests are certainly good alternatives with respect
to the traditional multivariate tests such as Hotelling
T2 and multivariate rank-based tests, especially in cases of
heavy-tailed distributions. Moreover, the NPC methodology
offers several advantages since it provides robust solutions
with respect to the true underlying random error distribution
and it is not affected by the problem of the loss of degrees
of freedom when keeping fixed the number of observations.
Indeed, unlike traditional methods, when the number
of informative variables increases its power monotonically
increases as well (leading to the so-called finite-sample
consistency property of NPC Test, Pesarin and Salmaso in
J. Nonparametr. Stat. 22(5):669–684, 2010b)
An empirical study on new product development process by nonparametric combination (NPC) testing methodology and post-stratification
No full textThis paper explores through an empirical application of NonParametric Combination (NPC) testing methodology, the different behaviours that distinguish those firms that develop successful products from those that are less successful. The NonParametric Combination (NPC) of dependent permutation tests methodology, particularly useful with observational studies and in presence of non-normal and/or categorical data, consists of an innovative testing method that allows the researcher to go beyond some usual testing constraints, such as the multivariate nature of most real problems and the relative small size of the available datasets
Metodi nonparametrici multivariati per l'analisi della composizione chimica di ceramiche antiche: il caso della ceramica di tipo etrusco padano veneta
No full textApplicazione dei test di permutazione per la valutazione e validazione di una prova linguistica
No full textFuture Trends on Global Performance Indicators in Industrial Research
No full textWithin the Research and Development activities, complex statistical problems of hypothesis testing can commonly arise. The complexity of the problem is mainly referred to the multivariate nature of the study and possibly to the presence of mixed performance variables (ordinal categorical, binary or continuous) and sometimes to missing values as well. In this contribution we consider permutation methods for multivariate testing on mixed variables within the framework of multivariate randomised complete block design. The novel approach we propose has been studied and validated via Monte Carlo simulation study. Finally we propose an application to real data, where several panellists from an R&D division of an home-care company are enrolled to studying several possible new fragrances of a given detergent to be compared with the own presently marketed product
A permutation solution for two-sample location-scale test
No full textThe aim of this work is to present and discuss a permutation solution for the two-sample location-scale testing problem by means of a simulation study. As suggested by the simulation results, we can confirm that the proposed solution is a good alternative to traditional procedures, such as the Lepage test. One of the greatest advantages of our permutation solution is that it has a good behaviour both under the null hypothesis and in power with small sample sizes. Hence, in each situation where the normality assumption may be hard to justify, this nonparametric procedure can be considered a valid solution
Valutazione di un nuovo servizio poliambulatoriale mediante tecniche di Conjoint Analysis
No full text- …
