Prior to the presentation of a test stimulus, subjects' attentional state was either narrowly focused on a particular location or broadly spread over a large spatial region. In previous studies, it was found that broadly spread attention enhances the sensitivity of relatively large spatial filters (increasing the perceiver's spatial scale), thereby diminishing spatial resolution and enhancing s...

We discuss the use of fixed and random effects models in the context of educational research and set out the assumptions behind the two modelling approaches. To illustrate the issues that should be considered when choosing between these approaches, we analyse the determinants of pupil achievement in primary school, using data from the Avon Longitudinal Study of Parents and Children. We conclude...

An alternative to the classical mixedmodel with normal random effects is to use a Dirichlet process to model the random effects. Such models have proven useful in practice, and we have observed a noticeable variance reduction, in the estimation of the fixed effects, when the Dirichlet process is used instead of the normal. In this paper we formalize this notion, and give a theoretical justifica...

In this paper I discuss economic processes that may give rise to spatial patterns in data, and explore the relative merits of alternative modeling approaches when data are spatially correlated. Specifically, I present an estimation scheme that allows for spatial random effects, and focus attention on cases in which such a framework may be preferred to the more general fixed effects framework th...

Time-hopping patterns can be constructed from simple difference sets. By studying such constructions, we prove that whenever n 2, n, n 1, or n + 1 is a prime power, then we can construct timehopping patterns that have n terms, and are of length less than n2. We show by computation that such patterns can have length less then n2 n’ for all n 5 150. We also show that time-hopping patterns of n te...

In this paper we consider the Anderson type model and show that the density of states is analytic in an interval for large disorder. The examples we have allow for the single site distributions to have some singular components. We also allow non-nearest neighbour hopping terms.