Search results for "STATISTICS"
showing 10 items of 7671 documents
Granulometric moments and corneal endothelium status
2001
Abstract Specular microscopy is a common practice in Ophthalmology. The corneal endothelium status is usually evaluated by means of the density, the hexagonality, the mean, the standard deviation and the coefficient of variation of cell areas. We propose to replace the cell area moments by the corresponding moments of a different probability distribution, the granulometric size distribution associated to a disc. All cells touching the frame are ignored by the area moments but used by the granulometric moments. Twenty images have been analyzed. When the size of the focused region is reduced, the area moments show a greater variation than the corresponding granulometric moments.
MORPHOMETRIC ANALYSIS OF HUMAN CORNEAL ENDOTHELIUM BY MEANS OF SPATIAL POINT PATTERNS
2002
This paper presents a method for detecting abnormalities in spatial arrangements of cells within any tissue that can be described by different sets of relevant points. The method has been applied to the detection of subtle abnormalities in corneal endothelia. Images of this type of tissue can be characterized by two types of points: cell centroids and triple points associated with the apical intersections as it was proposed by Díaz.7 Both types of points jointly considered are modeled using a bivariate spatial point process; then a statistical analysis based on certain distributional descriptors proposed by Doguwa4,9 is carried out to discriminate severe and subtle abnormalities from contr…
Measuring the Spatial Homogeneity in Corneal Endotheliums by Means of a Randomization Test
1999
Quantification of regularity of cell sizes and the spatial arrangement of cells in corneal endotheliums becomes of a great importance associated to stress situations such as cataract surgery, corneal transplantation or implantation of intra-ocular lenses. A new index of regularity of the spatial distribution of cell sizes in corneal endotheliums is proposed. The corneal endothelium is described by means of a spatial marked point pattern (the cell centroids marked with the cell areas). The hypothesis of no dependency between mark and locations is tested by a Monte Carlo test. The new index is the p-value of the test validating the hypothesis. Pairs of endotheliums from different eyes of the …
Identifying predictive factors in compliance with the COVID-19 containment measures: A mediation analysis
2021
Giusy Danila Valenti, Palmira Faraci Faculty of Human and Social Sciences, University of Enna âKoreâ, Enna, ItalyCorrespondence: Giusy Danila ValentiCittadella Universitaria, 94100, ItalyEmail giusy.valenti@unikore.itIntroduction: The outbreak of the COVID-19 pandemic has led governments to implement some containment measures to flatten the curve of the diffusion of the virus. The current study aims to investigate individual differences in compliance with these restrictive behaviors. In a sample of Italian individuals (N = 300), we examined whether sociodemographic factors, personality traits, fatalism, and fear could be considered as possible predictors.Methods: We performed a series o…
National level paths to the mining industry’s Social Licence to Operate (SLO) in Northern Europe: The case of Finland
2020
Abstract Research on the social licence to operate (SLO) has traditionally focused on local communities directly affected by mining operations. There has been a lack of systematic research exploring attitudes to mining among the public at large. Based on a national survey (N = 1091) of Finns’ attitudes towards mining conducted in 2016, we test a theoretical model using path analysis to examine the factors affecting the social licence to operate (SLO) of mining in Finland. The aim is to shed light on the factors affecting SLO at national level in Finland and to add to the growing body of research seeking to understand the mining industry’s SLO at national level in diverse social, economic an…
The Territorial Organization of Public Tourism Statistics in Spain: A Problem of Date Generation and Use in Geomarketing
2021
The changes produced in the last decade in tourism have generated new demands for statistical information that is comparable over time and space, on a microdata scale and focused on knowledge of tourist behaviour. However, the decentralization of the production of tourism statistics in Spain, derived from the division of powers between the Spanish state and the autonomous communities, has produced the emergence of various and multiple alternative entities for the generation and transfer of tourism data. This fragmentation produces a high dysfunctionality and inefficiency, due to, among other circumstances, a high heterogeneity and duplication of data, a heterogeneity of methodology and type…
A systematic comparison of kinetic modelling methods generating parametric maps for [11C]-(R)-PK11195
2006
[(11)C]-(R)-PK11195 is presently the most widely used radiotracer for the monitoring of microglia activity in the central nervous system (CNS). Microglia, the resident immune cells of the brain, play a critical role in acute and chronic diseases of the central nervous system and in host defence against neoplasia. The purpose of this investigation was to evaluate the reliability and sensitivity of five kinetic modelling methods for the formation of parametric maps from dynamic [(11)C]-(R)-PK11195 studies. The methods we tested were the simplified reference tissue model (SRTM), basis pursuit, a simple target-to-reference ratio, the Logan plot and a wavelet based Logan plot. For the reliabilit…
Inference for the interclass correlation in familial data using small sample asymptotics
2012
Inference on the parent-offspring correlation coefficient is an important problem in the analysis of familial data, and point estimates and likelihood based inference are available in the literature. In this work, corrections for the signed log-likelihood ratio test statistics are proposed, based on small sample asymptotics, in order to achieve accurate small sample performance. The corrected statistic can be used for hypothesis testing as well as for interval estimation.
Fractal dimension confidence interval estimation of epicentral distributions
1999
Estimates of the fractal dimension of hypocentral distributions require evaluating the range of independent variables in which fractal parameters exhibit a power law. Systematic and accidental errors are produced mainly by the subjective selection of this range, the insufficiency of data sets as well as by hypocenter mislocations. Therefore it is very important to determine the confidence intervals which are associated with fractal dimension estimates. The effects of various sources of errors are studied using different geometric clusters of epicenters, which have been synthetically generated using a multicluster algorithm with different hierarchical levels, so as to reproduce some characte…
Finite Sample Sizes of the GRS Test in the Presence of Dynamic Correlation and Conditional Heteroskedasticity
2017
This paper investigates the finite sample properties of the widely-used Gibbons, Ross, Shanken (1989) (GRS) test in the presence of both conditional correlation and conditional heteroskedasticity. It finds that the GRS test exhibits serious size distortions resulting in potentially misleading statistical inferences. The correct critical values, as reported in the study, are considerably larger than suggested by the GRS test.