EM algorithm Epsilon-skew-Cauchy Epsilon-skew-Normal Fisher information matrix Humanities Riesgo (Seguros) Seguros Social interaction Weibull censored data asymmetric bimodal distribution bimodal bimodality bivariate densities fitting distributions flexible skew-normal distribution generalized Cauchy distributions half-normal distribution identifiability kurtosis likelihood maximum likelihood maximum likelihood estimates maximum likelihood estimation moments normal distribution ordering positive and negative skewness power-normal distribution probabilistic distribution class skew Birnbaum–Saunders distribution