Department of Statistics, Article

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Purutçuoğlu Gazi, Vilda (27)
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Recent Submissions

An optimal stopping problem for spectrally negative Markov additive processes
Çağlar, Mine; Kyprianou, Andreas; Vardar Acar, Ceren (2021-07-01)
Previous authors have considered optimal stopping problems driven by the running maximum of a spectrally negative Lévy process as well as of a one-dimensional diffusion; see e.g. Kyprianou and Ott (2014); Ott (2014); Ott (...
Analysis of Confidence Levels and Application Success Rates in Simulator-Based Dental Anesthesia Education Among Undergraduate Dental Students
Vural, Çağıl; Bozkurt, Poyzan; Vardar Acar, Ceren; Üçok, Cahit (2021-06-01)
© 2021 American Association of Oral and Maxillofacial SurgeonsPurpose: We investigated the confidence levels of undergraduate dental students who used dental anesthesia simulators and patient reports of undergraduate denta...
The impacts of COVID-19 lockdown on PM10 and SO2 concentrations and association with human mobility across Turkey
ORAK, NUR HANİFE; Özdemir, Ozancan (2021-06-01)
© 2021 Elsevier Inc.The SARS-CoV-2 virus pandemic (COVID-19) has caused 2.25 million deaths worldwide by February 3, 2021 (JHU, 2021) and still causing severe health and economic disruptions with increasing rates. This stu...
Performance comparison of filtering methods on modelling and forecasting the total precipitation amount: a case study for Mugla in Turkey
NESLİHANOĞLU, SERDAR; ÜNAL, ECEM; Yozgatlıgil, Ceylan (2021-03-01)
Condensed water vapor in the atmosphere is observed as precipitation whenever moist air rises sufficiently enough to produce saturation, condensation, and the growth of precipitation particles. It is hard to measure the am...
Novel model selection criteria for LMARS: MARS designed for biological networks
Bulbul, Gul Bahar; Purutçuoğlu Gazi, Vilda (2021-03-01)
In higher dimensions, the loop-based multivariate adaptive regression splines (LMARS) model is used to build sparse and complex gene structure nonparametrically by correctly defining its interactions in the network. Also, ...
A study on the discretization of fractional Brownian motion
Coşkun, Buket; Vardar Acar, Ceren; Demirtaş, Hakan (2020-12-01)
In this study, we first discretize the fractional Brownian motion in time and observe multivariate Gaussian random variables (mGrv) to have a fractional Gaussian noise (fGn). Afterwards, we have discretized this discrete t...
Application of r-vine copula method in Istanbul stock market data: A case study for the construction sector
Farnoudkia, Hajar; Purutçuoğlu Gazi, Vilda (Ankara Yıldırım Beyazıt Üniversitesi , 2020-12-01)
In the stock market, the relationship between the sectorial changes can be very informative in order to predict the changes in prices of assets from each sector. In order to understand these sectorial relations, various st...
CD-vine model for capturing complex dependence
Ozan Evkaya, O.; Yozgatlıgil, Ceylan; Sevtap Selcuk-Kestel, A. (Informa UK Limited, 2020-10-26)
Copula based finite mixture models allow us to capture the dependence between random variables more flexibly. Although bivariate case of finite mixture models has been commonly studied, limited efforts have been spent on f...
Utility of lung ultrasound assessment for probable SARS-CoV-2 infection during pregnancy and universal screening of asymptomatic individuals
Kalafat, E.; Yassa, M.; Koc, A.; Tug, N. (Wiley, 2020-10-01)
Lung ultrasonography in pregnant women during the COVID-19 pandemic: an interobserver agreement study among obstetricians
Yassa, Murat; Mutlu, Memis Ali; Birol, Pinar; Kuzan, Taha Yusuf; Kalafat, Erkan; Usta, Canberk; Yavuz, Emre; Keskin, Ilkhan; Tug, Niyazi (Korean Society of Ultrasound in Medicine, 2020-10-01)
Purpose: This study investigated interobserver agreement in lung ultrasonography (LUS) in pregnant women performed by obstetricians with different levels of expertise, with confirmation by an expert radiologist.
Mutual information model selection algorithm for time series
Akca, Elif; Yozgatlıgil, Ceylan (Informa UK Limited, 2020-09-01)
Time series model selection has been widely studied in recent years. It is of importance to select the best model among candidate models proposed for a series in terms of explaining the procedure that governs the series an...
Parallel computing in linear mixed models
Gökalp Yavuz, Fulya; Schloerke, Barret (Springer Science and Business Media LLC, 2020-09-01)
In this study, we propose a parallel programming method for linear mixed models (LMM) generated from big data. A commonly used algorithm, expectation maximization (EM), is preferred for its use of maximum likelihood estima...
Is umbilicocerebral ratio better than cerebroplacental ratio for predicting adverse pregnancy and neonatal outcomes?
Kalafat, Erkan; Kalaylioglu, Zeynep; Thilaganathan, Basky; Khalil, Asma (Elsevier BV, 2020-09-01)
Objective A secondary analysis of the trial of randomized umbilical and fetal flow in Europe suggested that the umbilicocerebral ratio (UCR) provides better differentiation of neurodevelopmental outcome in the abnormal ra...
The role of aspirin in prevention of preeclampsia in twin pregnancies: does the dose matter?
Kalafat, Erkan; Shirazi, Amani; Thilaganathan, Basky; Khalil, Asma (Elsevier BV, 2020-09-01)
Objective The use of aspirin in twin pregnancies for the prevention of preeclampsia is a controversial topic, and evidence on the required dose of aspirin is scarce. We aimed to assess the efficacy of 75 mg/day vs 150 mg/...
Performance of Antenatal Diagnostic Criteria of Twin-Anemia-Polycythemia Sequence
Liu, Becky; Kalafat, Erkan; Bhide, Amar; Thilaganathan, Basky; Khalil, Asma (2020-09-01)
This study aims to elicit the validation performance of different diagnostic criteria and to evaluate the disease course and perinatal outcomes of pregnancies complicated by twin anemia polycythemia sequence (TAPS). Monoch...
The Association Between Hypertension in Pregnancy and Preterm Birth with Fetal Growth Restriction in Singleton and Twin Pregnancy: Use of Twin Versus Singleton Charts
Kalafat, Erkan; Abiola, Aisha; Thilaganathan, Basky; Bhide, Amar; Khalil, Asma (MDPI AG, 2020-8-5)
Objective: To compare the rates of fetal growth restriction (FGR) in singleton and twin pregnancies using singleton and twin-specific birthweight standards. Methods: The study included liveborn twin and singleton pregnanci...
Re: Ratio of umbilical and cerebral artery pulsatility indices in assessment of fetal risk: numerator and denominator matter
Kalafat, E.; Ozturk, E.; Kalaylioglu, Z.; Akkaya, Ayşen; Khalil, A. (Wiley, 2020-08-01)
Variable selection in elliptical linear mixed model
Gökalp Yavuz, Fulya; Arslan, Olcay (Informa UK Limited, 2020-08-01)
Variable selection in elliptical Linear Mixed Models (LMMs) with a shrinkage penalty function (SPF) is the main scope of this study. SPFs are applied for parameter estimation and variable selection simultaneously. The smoo...
Umbilicocerebral ratio: potential implications of inversing the cerebroplacental ratio
Kalafat, E.; Khalil, A. (Wiley, 2020-08-01)
Prognostic Value of Maternal Cardiovascular Hemodynamics in Women With Gestational Hypertension and Chronic Hypertension in Pregnancy
Kalafat, Erkan; Perry, Helen; Bowe, Sophie; Thilaganathan, Basky; Khalil, Asma (Ovid Technologies (Wolters Kluwer Health), 2020-08-01)
This study aimed to assess the prognostic value of cardiovascular assessment in women with gestational hypertension or chronic hypertension for the risk of preeclampsia and need for closer antenatal surveillance. This was ...
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