Often in biomedical studies, the routine use of linear mixed-effects models (based on Gaussian assumptions) can be questionable when the longitudinal responses are skewed in nature. Skew-normal/elliptical models are widely used in those situations. Often, those skewed responses might also be subjected to some upper and lower quantification limits (QLs; viz., longitudinal viral-load measures in ...

Finite mixtures of skew distributions provide a flexible tool for modelling heterogeneous data with asymmetric distributional features. However, parameter estimation via the Expectation-Maximization (EM) algorithm can become very timeconsuming due to the complicated expressions involved in the E-step that are numerically expensive to evaluate. A more time-efficient implementation of the EM algo...

The results of Waldman (1982) on the Normal-Half Normal stochastic frontier model are generalized using the theory of the Dirac delta (Dirac, 1930), and distribution-free conditions are established to ensure a stationary point in the likelihood as the variance of the inefficiency distribution goes to zero. Stability of the stationary point and "wrong skew" results are derived or simulated for c...

A mixture of coalesced generalized hyperbolic distributions (GHDs) is developed by joining a finite mixture of generalized hyperbolic distributions with a novel mixture of multiple scaled generalized hyperbolic distributions (MSGHDs). After detailing the development of the mixture of MSGHDs, which arises via implementation of a multidimensional weight function, the density of our coalesced dist...

 In this paper we consider a general setting of skew-symmetric distribution which was constructed by Azzalini (1985), and its properties are presented. A suitable empirical estimator for a skew-symmetric distribution is proposed. In data analysis, by comparing this empirical model with the estimated skew-normal distribution, we show that the proposed empirical model has a better fit in den...

Fast computation of two-dimensional (2-D) generalized discrete Fourier transforms (GDFTs) and generalized discrete Hartley transforms (GDHTs) are discussed in terms of a new method which is derived based on index permutation, linear congruences, and polynomial transforms. Further, the 2-D skew circular convolution computed by the proposed skew polynomial transform is also included. ( 2000 Elsev...