Efficienza dei terminali di trasporto intermodale strada-rotaia italiani

Come evidenziato da ampia letteratura relativa alle infrastrutture di trasporto, tra i fattori che ne caratterizzano l’efficienza vi sono elementi di forte variabilità legati alla posizione geografica ed alla inclusione in reti di scambio internazionale di merci. L’articolo intende verificare se tali fattori sono osservabili per i terminali intermodali strada-ferrovia italiani. Utilizzando modelli con dati panel di frontiera stocastica è stata stimata l’efficienza tecnica dei terminali selezionati e verificato se essa è significativamente influenzata da elementi, oltre che dimensionali, di contesto operativo e di mercato. Attenzione particolare è stata posta alla verifica dell’evoluzione dell’efficienza nel tempo e se l’efficienza tecnica ha risentito di effetti di progresso tecnologico nel periodo 2007-2011. Con riferimento a tale periodo temporale, di forte variabilità della domanda di trasporto intermodale strada-ferro in Italia, sono stati applicati diversi modelli econometrici per valutare l’efficienza tecnica dei terminali intermodali e studiarne il relativo trend evolutivo nel tempo. I risultati dello studio mostrano un progresso tecnologico che ha negativamente contribuito alla produttività dei terminali nel periodo e che tutti i modelli applicati allo scopo hanno riscontrato un declino nell’efficienza tecnica

Dimensionality reduction methods for contingency tables with ordinal variables

Correspondence analysis is a widely used tool for obtaining a graphical representation of the interdependence between the rows and columns of a contingency table, by using a dimensionality reduction of the spaces. The maximum information regarding the association between the two categorical variables is then visualized allowing to understand its nature. Several extensions of this method take directly into account the possible ordinal structure of the variables by using different dimensionality reduction tools. Aim of this paper is to present an unified theoretical framework of several methods of correspondence analysis with ordinal variables

Cumulative chi-squared statistics for the service quality improvement: new properties and tools for the evaluation

In service quality evaluation, data are often categorical variables with ordered categories and collected in two way contingency table. The Taguchi’s statistic is a measure of the association between these variables as a simple alternative to Pearson’s test. An extension of this statistic for three way contingency tables handled in two way mode is introduced.We highlight its several properties, the approximated distribution, a decomposition according to orthogonal quantities reflecting the main effects and the interaction terms, and an extension of cumulative correspondence analysis based on it

CATANOVA for ordinal variables using orthogonal polynomials with different scoring methods

In the context of categorical data analysis, the CATegorical ANalysis Of Variance (CATANOVA) has been proposed to analyse the scheme variable-factor, both for nominal and ordinal variables. This method is based on the C statistic and allows to test the statistical significance of the tau index using its relationship with the C statistic. Through Emerson orthogonal polynomials (EOP) a useful decomposition of C statistic into bivariate moments (location, dispersion and higher order components) has been developed. In the construction of EOP the categories are replaced by scores, typically natural scores. In the paper, we provide an overview of the main scoring schemes focusing on the advantages and the statistical properties; we pay special attention to the impact of the chosen scores on the C statistic of CATANOVA and the graphical representations of doubly ordered non-symmetrical correspondence analysis. Through a real data example, we show the impact of the scoring schemes and we consider the RV and multidimensional scaling as tools to measure similarity among the results achieved with each method

Weighted log ratio analysis by means of Poisson factor models: a case study to evaluate the quality of the public services offered to the citizens

In this paper we analyse the degree of dissatisfaction expressed by citizens regarding the quality of public services offered by municipalities in an average size city in the south of Italy. A previous study, carried out by multiple correspondence analysis, showed that the degree of dissatisfaction was closely linked to the age and education level of interviewed subjects, and the urban area (neighbourhood) in which they lived. On the basis of this result, we created two contingency tables. The first contingency, N , represents a cross classification of n dissatisfied individuals based upon three variables: Urban area (residential neighbourhood), age, and education. Taking population distribution (based on Age and Education) within each neighbourhood into account, we considered another table, S , which intersects the same variable and represents the target population. We started with a Goodman RC(M) association model, and obtained a weighted log ratio analysis. In particular, we propose a weighted log ratio analysis using Poisson factor models that explicitly considers count nature and automatically incorporates an offset. Moreover, we have compared the results of the log ratio analysis with and without offset by means of the RV coefficient

Some Interpretative Tools for Non-Symmetrical Correspondence Analysis

CATANOVA, Confidence circles, Goodman-Kruskal tau index, Linear constraints, Non-symmetrical correspondence analysis,

Efficienza dei terminali di trasporto intermodale strada-rotaia italiani

Come evidenziato da ampia letteratura relativa alle infrastrutture di trasporto, tra i fattori che ne caratterizzano l’efficienza vi sono elementi di forte variabilità legati alla posizione geografica ed alla inclusione in reti di scambio internazionale di merci. L’articolo intende verificare se tali fattori sono osservabili per i terminali intermodali strada-ferrovia italiani. Utilizzando modelli con dati panel di frontiera stocastica è stata stimata l’efficienza tecnica dei terminali selezionati e verificato se essa è significativamente influenzata da elementi, oltre che dimensionali, di contesto operativo e di mercato. Attenzione particolare è stata posta alla verifica dell’evoluzione dell’efficienza nel tempo e se l’efficienza tecnica ha risentito di effetti di progresso tecnologico nel periodo 2007-2011. Con riferimento a tale periodo temporale, di forte variabilità della domanda di trasporto intermodale strada-ferro in Italia, sono stati applicati diversi modelli econometrici per valutare l’efficienza tecnica dei terminali intermodali e studiarne il relativo trend evolutivo nel tempo. I risultati dello studio mostrano un progresso tecnologico che ha negativamente contribuito alla produttività dei terminali nel periodo e che tutti i modelli applicati allo scopo hanno riscontrato un declino nell’efficienza tecnica

Non-symmetric correspondence analysis and biplot representation: Comparing differences in market share distribution

Dependence structure, Non-symmetric Correspondence Analysis, Biplot, Symmetric plot, Market share differences,

Analysis of two-way ordinal contingency tables for social research

In the social research the variables often consist of ordered categories. When the row and column variables of a contingency table both are on ordinal scale, several techniques (Beh, 1997) have been proposed, most of which are based on the partition of Pearson’s chi-squared statistic. Recently doubly ordered cumulative correspondence analysis (D’ambra, Beh, Camminatiello, 2014) has been proposed by partitioning Hirotsu’s chi-squared statistic (Hirotsu, 1994). The association in these tables can be also described by using various types of odds ratios, among which, global odds ratios (Agresti, Coull, 2002). In this contribution we propose a modification of the above doubly ordered cumulative correspondence analysis based on the logarithms of the elements of the doubly cumulative table obtained by collapsing row and column classifications into dichotomies. By means of this generalization we can compute and represent the global odds ratios in the two-dimensional plot