Variance estimation for integrated population models

State-space models are widely used in ecology. However, it is well known that in practice it can be difficult to estimate both the process and observation variances that occur in such models. We consider this issue for integrated population models, which incorporate state-space models for population dynamics. To some extent, the mechanism of integrated population models protects against this problem, but it can still arise, and two illustrations are provided, in each of which the observation variance is estimated as zero. In the context of an extended case study involving data on British Grey herons, we consider alternative approaches for dealing with the problem when it occurs. In particular, we consider penalised likelihood, a method based on fitting splines and a method of pseudo-replication, which is undertaken via a simple bootstrap procedure. For the case study of the paper, it is shown that when it occurs, an estimate of zero observation variance is unimportant for inference relating to the model parameters of primary interest. This unexpected finding is supported by a simulation study.     

A Cross-National Analysis of Militarization and Well-Being Relationships in Developing Countries

We focus upon linkages between militarization and development in Third-World countries. The theoretical and empirical literature variously ascribes positive or negative developmental consequences to militarization. Part of this ambiguity results from an empirical focus solely on the impacts of national defense spending on growth in the gross national product. We expand our analysis to includethreecomponents of militarization (military regimes, participation in the military, and the importation of military hardware), as influences onthreeforms of national development (economic growth, accumulation of human capital, and growth in political rights). An important part of our analysis is the use of regression techniques that address the untoward consequences of a variety of regression problems, that are for the most part untreated in conventional analyses. We find with these techniques that militarization significantly impacts development in readily interpretable ways.     

Modelling cell generation times by using the tempered stable distribution

Summary.  We show that the family of tempered stable distributions has considerable potential for modelling cell generation time data. Several real examples illustrate how these distributions can improve on currently assumed models, including the gamma and inverse Gaussian distributions which arise as special cases. Our applications concentrate on the generation times of oligodendrocyte progenitor cells and the yeast Saccharomyces cerevisiae . Numerical inversion of the Laplace transform of the probability density function provides fast and accurate approximations to the tempered stable density, for which no closed form generally exists. We also show how the asymptotic population growth rate is easily calculated under a tempered stable model.