We consider the relative merits of various saddlepoint approximations for the c.d.f. of a statistic with a possibly non-normal limit distribution. In addition to the usual Lugannani-Rice approximation we also consider approximations based on higher-order expansions, including the case where the...

We derive saddlepoint approximations for the density and distribution functions of the half-life estimated by OLS from an AR(1) or AR(p) model. Our analytic results are used to prove that none of the integer-order moments of these half-life estimators exist. This provides an explanation for the...

Diffusion processes are widely used for modelling real-world phenomena. Except for select cases however, analytical expressions do not exist for a diffusion process’ transitional probabilities. It is proposed that the cumulant truncation procedure can be applied to predict the evolution of the...

Two recent examples of data from statistical consulting work form the basis of this paper. Both data sets arose from situations where temporal decay was expected, and different models for this are discussed, in particular, variants on simple exponential decay: hyperexponential (or mixed...