Showing papers by "Hammou El Barmi published in 2000"

Transformation- based density estimation For weighted distributions

Abstract: In this paper we consider the estimation of a density f on the basis of random sample from a weighted distribution G with density g given by ,where w(u) > 0 for all u and . A special case of this situation is that of length-biased sampling, where w(x) = x. In this paper we examine a simple transformation-based approach to estimating the density f. The approach is motivated by the form of the nonparametric estimator maximum likelihood of f in the same context and under a monotonicity constraint. Since the method does not depend on the specific density estimate used (only the transformation), it can be used to construct both simple density estimates (histograms or frequency polygons) and more complex methods with favorable properties (e.g., local or penalized likelihood estimates). Monte Carlo simulations indicate that transformation-based density estimation can outperform the kernel-based estimator of Jones (1991) depending on the weight function w, and leads to much better estimation of monotone densities...

Testing ordered hypotheses in animal resource selection studies

Abstract: Many studies on animal resource selection involve recording the number of times radio-collared animals are observed in a finite number of resource categories (e.g., habitats). A general objective of these studies is to determine if the animals are using resources disproportionately to resource availability. In this paper, we propose testing ordered resource selections. The advantage of testing ordered resource selections hypotheses is that a researcher can evaluate specific resource selection relationships beyond the multiple comparison testing framework. We use order-restricted inference theory to construct estimators and hypothesis tests for these types of resource selection tests. Detailed illustrations using data from a radio-tracking study on gray partridges illustrate the techniques.