On the definition of a concentration function relevant to the ROC curve

This work provides a definition of concentration curve alternative to the one presented on this journal by Schechtman and Schechtman (Metron 77:171–178, 2019). Our definition clarifies, at the population level, the relationship between concentration and the omnipresent ROC curve in diagnostic and classification problems

Concentration and ROC Curves, Revisited

This work is aimed at illustrating the strict relationship between a general definition of concentration function appeared quite some time ago on this journal and a widely used measure of the diagnostic strength of a family of binary classifiers indexed by a threshold parameter, the so-called ROC curve. The ROC curve is a common work tool in Statistics, Machine Learning and Artificial Intelligence, appearing in many applications where a binary classification (diagnosis) procedure is of interest. Hence, it is worth remarking that diagnostic strength and concentration are two sides of the same coin: the higher the concentration of one probability measure with respect to another, the higher the diagnostic strength of the likelihood ratio classification rule

Equality of opportunity and optimal cash and in-kind policies

Este trabajo examina el argumento para la provisión pública de ciertos bienes privados (e.g. educación y salud) basado en igualdad de oportunidades, mediante el estudio de la frontera de posibilidades de utilidad en una sociedad donde hay preferencias por la distribución de estos bienes. Cierto nivel de calidad de servicios de educación o salud se puede consumir gratis en el sector público, pero los individuos pueden optar por obtener dichos servicios del sector privado. Algunas de las conclusiones son: (i) una transferencia pura de efectivo es óptima cuando la redistribución de utilidad es suficientemente grande o pequeña; (ii) sí y sólo si tanto la preferencia de igualdad de oportunidades y la redistribución de utilidad son lo suficientemente grandes se puede justificar un programa en especie para toda la población; y (iii) aun cuando todos eligen este programa, puede ser óptimo hacer más redistribución aumentando el tamaño del programa.This paper examines the argument for public provision of certain private goods, like education and health, based on equality of opportunity by studying the utility possibility frontier of a society in which there is a concern for the distribution of these goods. A given quality of education or health services can be consumed for free in the public sector, but people can opt-out and purchase their desired quality levels in the private sector. Some of the conclusions are: (i) a pure cash transfer is optimal when the utility redistribution is either "sufficiently" small or large; (ii) if and only if both the equality-of-opportunity concern and the utility redistribution are large enough, can an in-kind program which attracts the whole population be justified; (iii) even when everybody chooses the in-kind program, it may be optimal to perform some additional utility redistribution by increasing the size of such program.Trabajo publicado en el Journal of Public Economics 90 (1-2): 143-169, January, 2006.Centro de Estudios Distributivos, Laborales y Sociales (CEDLAS

Equality of opportunity and optimal cash and in-kind policies

Este trabajo examina el argumento para la provisión pública de ciertos bienes privados (e.g. educación y salud) basado en igualdad de oportunidades, mediante el estudio de la frontera de posibilidades de utilidad en una sociedad donde hay preferencias por la distribución de estos bienes. Cierto nivel de calidad de servicios de educación o salud se puede consumir gratis en el sector público, pero los individuos pueden optar por obtener dichos servicios del sector privado. Algunas de las conclusiones son: (i) una transferencia pura de efectivo es óptima cuando la redistribución de utilidad es suficientemente grande o pequeña; (ii) sí y sólo si tanto la preferencia de igualdad de oportunidades y la redistribución de utilidad son lo suficientemente grandes se puede justificar un programa en especie para toda la población; y (iii) aun cuando todos eligen este programa, puede ser óptimo hacer más redistribución aumentando el tamaño del programa.This paper examines the argument for public provision of certain private goods, like education and health, based on equality of opportunity by studying the utility possibility frontier of a society in which there is a concern for the distribution of these goods. A given quality of education or health services can be consumed for free in the public sector, but people can opt-out and purchase their desired quality levels in the private sector. Some of the conclusions are: (i) a pure cash transfer is optimal when the utility redistribution is either "sufficiently" small or large; (ii) if and only if both the equality-of-opportunity concern and the utility redistribution are large enough, can an in-kind program which attracts the whole population be justified; (iii) even when everybody chooses the in-kind program, it may be optimal to perform some additional utility redistribution by increasing the size of such program.Trabajo publicado en el Journal of Public Economics 90 (1-2): 143-169, January, 2006.Centro de Estudios Distributivos, Laborales y Sociales (CEDLAS

Platygonus sp. (Mammalia: Tayassuidae) in Uruguay (Raigón? Formation; Pliocene–early Pleistocene), comments about its distribution and palaeoenvironmental significance in South America

This study provides the first record of Platygonus in Uruguay (Raigón? Formation, Pliocene–early Pleistocene; Canelones Department). The allocation to the Raigón Formation is tentative because the remains were found in a drill core. It is the oldest record of a tayassuid in Uruguay. The following morphological features clearly indicate that it belongs to Platygonus: simple premolars that are bicuspid, bunolophodont, mesodont and with an enamel cingulum surrounding the entire tooth. This is one of the largest forms among North American and South American Platygonus. The record of Platygonus in the Raigón Formation suggests arid or semi-arid climates, and, as do some associated birds and mammals, open or relatively open environments. A significant level of specific diversity of Platygonus in South America is recognized during the late Pliocene with the lowest diversity occurring during the early–middle Pleistocene.Fil: Gasparini, Germán Mariano. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. División Paleontología Vertebrados; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Ubilla, M.. Universidad del Uruguay. Facultad de Ciencias; Urugua

Exact and Asymptotic Inference in Clinical Trials with Small Event Rates under Inverse Sampling

In this paper we discuss statistical inference for a two-by-two table under inverse sampling, where the total number of cases is fixed by design. We demonstrate that the exact unconditional distributions of some relevant statistics differ from the distributions under conventional sampling, where the sample size is fixed by design. This permits us to define a simple unconditional alternative to Fisher’s exact test. We provide an asymptotic argument including simulations to demonstrate that there is little power-loss associated with the alternative test when the expected response rates are rare. We then apply the method to design a clinical trial in cataract surgery, where a rare side effect occurs in one in one-thousand patients. Objective of the trial is to demonstrate that adjuvant treatment with an antibiotic will reduce this risk to one in two-thousand. We use an inverse sampling design and demonstrate how to set this up in a sequential manner. Particularly simple stopping rules can be defined when using the unconditional alternative to Fisher’s exact test

Performance of a large limited streamer tube cell in drift mode

The performance of a large (3x3 $cm^2$) streamer tube cell in drift mode is shown. The detector space resolution has been studied using cosmic muons crossing an high precision silicon telescope. The experimental results are compared with a GARFIELD simulation.Comment: 18 pages, 7 figures. Accepted by Nucl. Instr. and Methods

Pitch-Luminance Crossmodal Correspondence in the Baby Chick: An Investigation on Predisposed and Learned Processes.

Our senses are constantly reached by a multitude of stimuli from all different sensory modalities. To create a coherent representation of the environment, we must integrate the various unimodal inputs that refer to the same object into a single multimodal representation. In some cases, however, we tend to bind certain properties of the stimuli without any apparent reason, which is a phenomenon named crossmodal correspondence. For instance, we match a spiky or a rounded shape with the sound "Kiki" or "Bouba", respectively. Similarly, we associate the left hemispace with low luminance and the right one with high luminance. Instances of crossmodal correspondences were described also in other mammals, and recently, a case of space-luminance crossmodal correspondence was reported in birds (i.e., domestic chicks). Here, we investigate the presence of pitch-luminance crossmodal correspondence in three-day-old chicks, employing experimental methods that exploit either predisposed or learned processes. While failing to report evidence for this phenomenon, we discuss the difference between statistical and structural crossmodal correspondences and the possible role of environmental factors in determining their emergence. Moreover, we discuss the importance of the different experimental methodologies to investigate distinct aspects of this perceptual phenomenon to reach a deeper understanding and unveil the role of innate vs. learned mechanisms