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Ayşen Akkaya

Department of Statistics
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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)
Adaptive estimation of autoregressive models under long-tailed symmetric distribution
Yentür, Begüm; Bayrak, Özlem Türker; Akkaya, Ayşen (2019-07-08)
Inference of Autoregressive Model with Stochastic Exogenous Variable Under Short-Tailed Symmetric Distributions
Bayrak, Ozlem Tuker; Akkaya, Ayşen (2018-12-01)
In classical autoregressive models, it is assumed that the disturbances are normally distributed and the exogenous variable is non-stochastic. However, in practice, short-tailed symmetric disturbances occur frequently and ...
Robust pairwise multiple comparisons under short-tailed symmetric distributions
Balci, Sibel; Akkaya, Ayşen (2015-11-02)
In one-way ANOVA, most of the pairwise multiple comparison procedures depend on normality assumption of errors. In practice, errors have non-normal distributions so frequently. Therefore, it is very important to develop ro...
Modified maximum likelihood estimators using ranked set sampling
Balci, Sibel; Akkaya, Ayşen; Ulgen, B. Emre (2012-01-15)
The closed-form maximum likelihood estimators (MLEs) of population mean and variance under ranked set sampling (RSS) do not exist since the likelihood equations involve nonlinear functions and have usually no explicit solu...
Can We Assess and Monitor Privacy and Security Risk for Social Networks?
Sahinoglu, Mehmet; Akkaya, Ayşen; Ang, David (2012-01-15)
Tiku, Moti L.; Akkaya, Ayşen (2010-01-10)
Modified maximum likelihood estimators of the parameters in a second order polynomial regression model are derived. They are shown to be considerably more efficient and robust than the commonly used least squares estimator...
Short-tailed distributions and inliers
Akkaya, Ahmet; Akkaya, Ayşen (Springer Science and Business Media LLC, 2008-08-01)
We consider two families of short-tailed distributions (kurtosis less than 3) and discuss their usefulness in modeling numerous real life data sets. We develop estimation and hypothesis testing procedures which are efficie...
Autoregressive models with short-tailed symmetric distributions
Akkaya, Ayşen; Tiku, Moti L. (Informa UK Limited, 2008-01-01)
Symmetric short-tailed distributions do indeed occur in practice but have not received much attention particularly in the context of autoregression. We consider a family of such distributions and derive the modified maximu...
Modified maximum likelihood estimators for autoregressive models
Akkaya, Ayşen; Tiku, ML (Informa UK Limited, 2005-06-20)