Person: Franco Pereira, Alba María
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First Name
Alba María
Last Name
Franco Pereira
Affiliation
Universidad Complutense de Madrid
Faculty / Institute
Ciencias Matemáticas
Department
Estadística e Investigación Operativa
Area
Estadística e Investigación Operativa
Identifiers
13 results
Search Results
Now showing 1 - 10 of 13
Item A fast epigraph and hypograph-based approach for clustering functional data(Statistics and computing, 2023) Pulido, Belén ; Franco Pereira, Alba María; Lillo, RosaClustering techniques for multivariate data are useful tools in Statistics that have been fully studied in the literature. However, there is limited literature on clustering methodologies for functional data. Our proposal consists of a clustering procedure for functional data using techniques for clustering multivariate data. The idea is to reduce a functional data problem into a multivariate one by applying the epigraph and hypograph indexes to the original curves and to their first and/or second derivatives. All the information given by the functional data is therefore transformed to the multivariate context, being informative enough for the usual multivariate clustering techniques to be efficient. The performance of this new methodology is evaluated through a simulation study and is also illustrated through real data sets. The results are compared to some other clustering procedures for functional data.- Project number: 233
Item Internacionalización de los estudios de másteres en Matemáticas: un paso adelante(2020) Gallardo Gutiérrez, Eva Antonia; Cimadevilla Rodríguez, Francisco Javier; Franco Pereira, Alba María; Vitoriano, Begoña; Arrondo Esteban, Enrique; Oleaga Apadula, Gerardo Enrique; Fenoy Muñoz, María del Mar - Project number: 082
Item Recursos interactivos para prácticas con Software Estadístico en Informática(2018) Franco Pereira, Alba María; Landaburu, Elena; Prieto Martínez, Juan José; Ramos Domínguez, Rosa María; Vadillo Muñoz, Óscar Item Inference on the symmetry point-based optimal cut-off point and associated sensitivity and specifcity with application to SARS-CoV-2 antibody data(Sort, 2023) Franco Pereira, Alba María; Pardo Llorente, M. Del Carmen; Nakas, C.T.; Reiser, B.In the presence of a continuous response test/biomarker, it is often necessary to identify a cut-off point value to aid binary classification between diseased and non-diseased subjects. The symmetry-point approach which maximizes simultaneously both types of correct classification is one way to determine an optimal cut-off point. In this article, we study methods for constructing confidence intervals independently for the symmetry point and its corresponding sensitivity, as well as respective joint nonparametric confidence regions. We illustrate using data on the generation of antibodies elicited two weeks post-injection after the second dose of the Pfizer/BioNTech vaccine in adult healthcare workers.Item Comparing quantile residual life functions by confidence bands(Lifetime data analysis, 2012) Franco Pereira, Alba María; Lillo Rodríguez, Rosa Elvira; Romo, JuanIn this article we present a nonparametric method for constructing confidence bands for the difference of two quantile residual life (qrl) functions. These bands provide evidence for two random variables ordering with respect to the qrl order. The comparison of qrl functions is of importance, specially in the treatment of cancer when there exists a possibility of benefiting from a new secondary therapy. A qrl function is the quantile of the remaining life of a surviving subject, as it varies with time. We show the applicability of this approach in Medicine and Ecology. A simulation study has been carried out to evaluate and illustrate the performance and the consistency of this new methodology.Item Non Parametric ROC Summary Statistics(REVSTAT Statistical Journal, 2017) Pardo Llorente, M. Del Carmen; Franco Pereira, Alba MaríaReceiver operating characteristic (ROC) curves are useful statistical tools for medical diagnostic testing. It has been proved its capability to assess diagnostic marker’s ability to distinguish between healthy and diseased subjects and to compare different diagnostic markers. In this paper we introduce non parametric ROC summary statistics to assess a ROC curve across the entire range of F P F s ∈ (0, 1) as well as over a restricted range of F P F s and compare them with some existing ones through a simulation study and through some real data examples. We also show their capability to compare two diagnostic markers.Item The decreasing percentile residual life ageing notion(Statistics, 2012) Franco Pereira, Alba María; Lillo Rodríguez, Rosa Elvira; Shaked, MosheEarlier researchers have studied some aspects of the classes of distribution functions with decreasing alpha-percentile residual life (DPRL(alpha)), 0 < alpha < 1. The purpose of this paper is to note some further properties of these classes, and to initiate a theory of non-parametric statistical estimation of DPRL(alpha) functions. Specifically, the close relationship between the DPRL(alpha) and the increasing failure rate ageing notions is studied. Other close relationships, between the DPRL(alpha) ageing notions and the percentile residual life stochastic orders, are described, and further properties of the above classes of distributions are derived. Finally, we introduce an estimator of the percentile residual life function, under the condition that it decreases, and we prove its strongly uniform consistency.Item Estimation of a monotone percentile residual life function under random censorship(Biometrical journal, 2013) Franco Pereira, Alba MaríaIn this paper, we introduce a new estimator of a percentile residual life function with censored data under a monotonicity constraint. Specifically, it is assumed that the percentile residual life is a decreasing function. This assumption is useful when estimating the percentile residual life of units, which degenerate with age. We establish a law of the iterated logarithm for the proposed estimator, and its n-equivalence to the unrestricted estimator. The asymptotic normal distribution of the estimator and its strong approximation to a Gaussian process are also established. We investigate the finite sample performance of the monotone estimator in an extensive simulation study. Finally, data from a clinical trial in primary biliary cirrhosis of the liver are analyzed with the proposed methods. One of the conclusions of our work is that the restricted estimator may be much more efficient than the unrestricted one.Item The percentile residual life up to time t(o): Ordering and aging properties(Journal of Statistical Planning and Inference, 2011) Franco Pereira, Alba María; Lillo Rodríguez, Rosa Elvira; Romo, JuanMotivated by practical issues, a new stochastic order for random variables is introduced by comparing all their percentile residual life functions until a certain instant. Some interpretations of these stochastic orders are given, and various properties of them are derived. The relationships to other stochastic orders are studied and also an application in reliability theory is described. Finally, we present some characterization results of the decreasing percentile residual life up to time to aging notion.Item The total time on test transform and the decreasing percentile residual life aging notion(Statistical methodology, 2014) Franco Pereira, Alba María; Shaked, MosheRecently Nair and Sankaran (2013) listed some known characterizations of common aging notions in terms of the total time on test transform (TTT) function. They also derived some new characterizations. The purpose of this note is to add two characterizations of the decreasing percentile residual life of order alpha (DPRL(alpha)) aging notion in terms of the TTT function, and in terms of the observed TIT when X is observed.