The main contents of this paper is two-fold.First, we present a method to approximate multivariate convex functions by piecewise linear upper and lower bounds.We consider a method that is based on function evaluations only.However, to use this method, the data have to be convex.Unfortunately,...

Wilks' lambda and the corresponding Wilks' distribution are well known concepts in testing in multivariate regression models.The topic of this paper is a generalization of the Wilks distribution.This generalized Wilks' distribution is relevant for testing in multivariate regression models with...

In a stationary sequence of random variables, high-threshold exceedances may cluster together.Two approximations of such a clusters distribution are established.These justify and generalize sampling schemes for clusters of extremes already known for Markov chains.

The copula function is considered within the context of financial multivariate data sets that are not normally distributed. The Bernstein polynomial approximation to copulae is given and motivated by its desirable properties. The multivariate convergence properties are analysed. The concept of...

Research over two decades has advanced the knowledge of how to assess predictive validity. We believe this has value to information systems (IS) researchers. To demonstrate, we used a widely cited study of IS spending. In that study, price-adjusted diffusion models were proposed to explain and...

Given a sequence (s0; s1,..., sN) of observations from a finite set S, we construct a process (sn)n_N that satisfies the following properties: (i) (Sn)n_ ·N is a piecewise Markov chain, (ii) the conditional distribution of sn given S0,...,Sn-1 is close to the empirical transition given by the...