Elif F. Acar

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The study of dependence between random variables is a mainstay in statistics. In many cases, the strength of dependence between two or more random variables varies according to the values of a measured covariate. We propose inference for this type of variation using a conditional copula model where the copula function belongs to a parametric copula family(More)
Any multivariate density can be decomposed through successive conditionings into basic building blocks involving only pairs of variables. The various ways in which this can be done are called regular vines; C-vines and D-vines are prime examples of such structures. A pair-copula construction (PCC) is a modelling strategy in which conditional and(More)
Motivated by genetic association studies of SNPs with genotype uncertainty, we propose a generalization of the Kruskal-Wallis test that incorporates group uncertainty when comparing k samples. The extended test statistic is based on probability-weighted rank-sums and follows an asymptotic chi-square distribution with k - 1 degrees of freedom under the null(More)
Germ cell tumors comprise 0.4-3.1% of all intracranial tumors, and teratoma constitutes 9-30% of them. Congenital intracranial tumors are very rare and only account for 0.5-1.5% of all childhood brain tumors. The most common type of these tumors present at birth is teratomas, which represent 0.5% of all intracranial tumors. Most teratomas are midline tumors(More)
The aim of this study was to investigate the role of serum cholinesterase (SChE) activity and S100B protein in the evaluation of patients with acute organophosphate (OP) poisoning. Patients with acute OP poisoning admitted to the emergency department were included in this cross-sectional study. Twenty healthy volunteers served as controls. The SChE activity(More)
PURPOSE To determine the effect of intraocular lens (IOL) type and anterior capsulectomy technique on the incidence of posterior capsule opacification. SETTING Department of Ophthalmology, Medical Faculty, University of Ondokuz Mayis, Samsun, Turkey. METHODS Three hundred two eyes of 294 patients were examined retrospectively after IOL implantation in(More)
Abstract: In conditional copula models, the copula parameter is deterministically linked to a covariate via the calibration function. The latter is of central interest for inference and is usually estimated nonparametrically. However, in many applications it is scientifically important to test whether the calibration function is constant or not. Moreover, a(More)
This article proposes a modeling strategy to infer the impact of a covariate on the dependence structure of right-censored clustered event time data. The joint survival function of the event times is modeled using a conditional copula whose parameter depends on a cluster-level covariate in a functional way. We use a local likelihood approach to estimate the(More)
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