SORT : Statistics and Operations Research Transactions
SORT (ISSN 1696-2281 / ISSN electrònic 2013-8830) és una publicació semestral d'àmbit internacional coeditada per l'Idescat i quatre universitats catalanes (Universitat Politècnica de Catalunya, Universitat de Barcelona, Universitat Autònoma de Barcelona i Universitat de Girona) i amb la col•laboració de la Regió Espanyola de la Societat Internacional de Biometria. Publicada íntegrament en anglès (amb resums en català), promou la publicació d'articles originals d'estadística aplicada i metodologia estadística, investigació operativa, estadística oficial i biometria, així com la recensió de llibres i altres publicacions en aquests àmbits. SORT es publica des del 2003 i representa la tercera sèrie de Qüestiió (Quaderns d'Estadística i Investigació Operativa), publicada per l'Idescat des del 1992.
Darreres entrades:
2013-11-11
15:57

14 p, 1.6 MB
Flexible quantile regression models : application to the study of the purple sea urchin / Martínez-Silva, Isabel (Universidade de Santiago de Compostela. Departamento de Estatística) ; Roca-Pardiñas, Javier (Universidade de Vigo. Departamento de Estatística) ; Lustres-Pérez, Vicente (Universidade de Santiago de Compostela. Departamento de Zoología y Antropología Física) ; Lorenzo-Arribas, Altea (Universidade de Santiago de Compostela. Departamento de Estatística) ; Cadarso-Suárez, Carmen (Universidade de Santiago de Compostela. Departamento de Estatística)
In many applications, it is often of interest to assess the possible relationships between covariates and quantiles of a response variable through a regression model. In some instances, the effects of continuous covariates on the outcome are highly nonlinear. [...]
has to take such flexible smooth effects into account. In this work, various flexible quantile regression techniques were reviewed and compared by simulation. Finally, all the techniques were used to construct the overall zone specific reference curves of morphologic measures of sea urchin Paracentrotus lividus (Lamarck, 1816) located in NW Spain.

2013
SORT : statistics and operations research transactions, Vol. 37, Núm. 1 (January-June 2013) , p. 81-94  ;
 Accés restringit a la UAB
2013-11-11
15:53

22 p, 3.5 MB
New insights into evaluation of regression models through a decomposition of the prediction errors : application to near-infrared spectral data / Sánchez-Rodríguez, María Isabel (Universidad de Córdoba. Departamento de Estadística, Econometría) ; Sánchez-López, Elena (Universidad de Córdoba. Departamento de Química Orgánica) ; Caridad, José Mª (Universidad de Córdoba. Departamento de Estadística, Econometría) ; Marinas, Alberto (Universidad de Córdoba. Departamento de Química Orgánica) ; Marinas, Jose Mª (Universidad de Córdoba. Departamento de Química Orgánica) ; Urbano, Francisco José (Universidad de Córdoba. Departamento de Química Orgánica)
This paper analyzes the performance of linear regression models taking into account usual criteria such as the number of principal components or latent factors, the goodness of fit or the predictive capability. [...]
the degree of multicollinearity and a decomposition of the mean squared error of the prediction which determines the nature, systematic or random, of the prediction errors. The applications use real data of extra-virgin oil obtained by near-infrared spectroscopy. [...]

2013
SORT : statistics and operations research transactions, Vol. 37, Núm. 1 (January-June 2013) , p. 57-78  ;
 Accés restringit a la UAB
2013-11-11
15:39

28 p, 389.4 KB
The normal distribution in some constrained sample spaces / Mateu-Figueras, Glòria (Universitat de Girona. Departament d’Informàtica i Matemàtica Aplicada) ; Pawlowsky-Glahn, Vera (Universitat de Girona. Departament d’Informàtica i Matemàtica Aplicada) ; Egozcue, Juan-José (Universitat Politècnica de Catalunya. Departament de Matemàtica Aplicada III)
Phenomena with a constrained sample space appear frequently in practice. This is the case, for example, with strictly positive data, or with compositional data, such as percentages or proportions. If the natural measure of difference is not the absolute one, simple algebraic properties show that it is more convenient to work with a geometry different from the usual Euclidean geometry in real space, and with a measure different from the usual Lebesgue measure, leading to alternative models that better fit the phenomenon under study. [...]
2013
SORT : statistics and operations research transactions, Vol. 37, Núm. 1 (January-June 2013) , p. 29-56  ;
 Accés restringit a la UAB
2013-11-11
15:32

10 p, 158.9 KB
A note on the Fisher information matrix for the skew-generalized-normal model / Arellano-Valle, Reinaldo B. (Pontificia Universidad Católica de Chile. Departamento de Estadística) ; Gómez, Héctor W. (Universidad de Antofagasta (Chile). Departamento de Matemáticas) ; Salinas, Hugo S. (Universidad de Atacama (Chile). Departamento de Matemática)
In this paper, the exact form of the Fisher information matrix for the skew-generalized normal (SGN) distribution is determined. The existence of singularity problems of this matrix for the skewnormal and normal particular cases is investigated. [...]
2013
SORT : statistics and operations research transactions, Vol. 37, Núm. 1 (January-June 2013) , p. 19-28  ;
 Accés restringit a la UAB
2013-11-11
15:25

16 p, 204.7 KB
Improved entropy based test of uniformity using ranked set samples / Mahdizadeh, Mahdi ; Arghami, Nasser Reza (Ferdowsi University of Mashhad. Department of Statistics, School of Mathematical Sciences)
Ranked set sampling (RSS) is known to be superior to the traditional simple random sampling (SRS) in the sense that it often leads to more efficient inference procedures. Basic version of RSS has been extensively modified to come up with schemes resulting in more accurate estimators of the population attributes. [...]
and MSRSS designs. A Monte Carlo simulation study is carried out to compare the power of the proposed tests under several alternative distributions with the ordinary test based on SRS. The results report that the new entropy tests have higher power than the original one for nearly all sample sizes and under alternatives considered.

2013
SORT : statistics and operations research transactions, Vol. 37, Núm. 1 (January-June 2013) , p. 3-18  ;
 Accés restringit a la UAB
2013-01-09
20:12

10 p, 2.8 MB
Flexible geoadditive survival analysis of non-Hodgkin lymphoma in Peru / Flores, Claudio (Universitat Politècnica de Catalunya. Departament de Estadística) ; Rodríguez-Girondo, Mar (Universitat de Vigo. Grup de Recerca SiDOR) ; Cadarso-Suárez, Carmen (Universidad de Santiago de Compostela. Departamento de Estadística) ; Kneib, Thomas (Georg August University. Department of Economics) ; Gómez, Guadalupe (Universitat Politècnica de Catalunya. Departament de Estadística) ; Casanova, Luis (Instituto Nacional de Enfermedades Neoplásicas (Lima, Perú))
Knowledge of prognostic factors is an important task for the clinical management of Non Hodgkin Lymphoma (NHL). In this work, we study the variables affecting survival of NHL in Peru by means of geoadditive Cox-type structured hazard regression models while accounting for potential spatial correlations in the survival times. [...]
2012
SORT : statistics and operations research transactions, Vol. 36, Núm. 2 (juliol-desembre 2012) , p. 221-230  ;
 Accés restringit a la UAB
2013-01-09
19:59

24 p, 224.6 KB
Statistical modelling and forecasting of outstanding liabilities in non-life insurance / Martínez-Miranda, María Dolores (Universidad de Granada. Departamento de Estadística) ; Perch Nielsen, Jens (City University (London). Cass Business School) ; Wüthrich, Mario V. (ETH Zurich, RiskLab. Department of Mathematics)
Non-life insurance companies need to build reserves to meet their claims liability cash flows. They often work with aggregated data. Recently it has been suggested that better statistical properties can be obtained when more aggregated data are available for statistical analysis than just the classical aggregated payments. [...]
2012
SORT : statistics and operations research transactions, Vol. 36, Núm. 2 (juliol-desembre 2012) , p. 195-218  ;
 Accés restringit a la UAB
2013-01-09
19:48

14 p, 403.0 KB
Hurdle negative binomial regression model with right censored count data / Ehsan Saffari, Seyed (Universiti Teknologi Malaysia. Department of Mathematics, Faculty of Science) ; Adnan, Robiah (Universiti Teknologi Malaysia. Department of Mathematics, Faculty of Science) ; Greene, William (New York University. Department of Economics, Stern School of Business)
A Poisson model typically is assumed for count data. In many cases because of many zeros in the response variable, the mean is not equal to the variance value of the dependent variable. Therefore, the Poisson model is no longer suitable for this kind of data. [...]
2012
SORT : statistics and operations research transactions, juliol-desembre 2012, p. 181-194  ;
 Accés restringit a la UAB
2013-01-09
19:29

28 p, 632.5 KB
The new class of Kummer beta generalized distributions / Pescim, R. R. (Universidade de Sao Paulo-USP. Departamento de Ciências Exatas) ; Cordeiro, G. M. (Universidade Federal de Pernambuco-UFPE. Departamento de Estatística) ; Demétrio, C. G. B. (Universidade de Sao Paulo-USP. Departamento de Ciências Exatas) ; Ortega, E. M. M. (Universidade de Sao Paulo-USP. Departamento de Ciências Exatas) ; Nadarajah, S. (University of Manchester. School of Mathematics)
Ng and Kotz (1995) introduced a distribution that provides greater flexibility to extremes. We define and study a new class of distributions called the Kummer beta generalized family to extend the normal, Weibull, gamma and Gumbel distributions, among several other well-known distributions. [...]
2012
SORT : statistics and operations research transactions, Vol. 36, Núm. 2 (juliol-desembre 2012) , p. 153-180  ;
 Accés restringit a la UAB
2013-01-09
18:41

14 p, 143.5 KB
A note on the use of supply-use tables in impact analyses / Lenzen, Manfred (The University of Sydney) ; Rueda-Cantuche, José M. (Universidad Pablo de Olavide (Sevilla))
Little attention has so far been paid to the problems inherent in interpreting the meaning of results from standard impact analyses using symmetric input-output tables. Impacts as well as drivers of these impacts must be either of the product type or of the industry type. [...]
2012
SORT : statistics and operations research transactions, Vol. 36, Núm. 2 (juliol-desembre 2012) , p. 139-152  ;
 Accés restringit a la UAB