We take a well-known dynamic model of an isolated, unstructured population and modify this to include a factor that allows for a reduction in fitness due to declining population sizes, often termed an Allee effect. Analysis of the behaviour of this model is carried out on two fronts - determining the equilibrium values and examining the stability of these equilibria. Our results point to the st...

Agreement between physicians in their classification of items such as mammograms for the presence of disease is an important tool in assessing the reliability of a diagnostic procedure, and the modeling of agreement data is a popular topic in the biomedical and social sciences. Interest often lies in assessing agreement in the underlying diagnostic procedure and making inferences for the popula...

Several codon-based methods are available for detecting adaptive evolution in protein-coding sequences, but to date none specifically identify sites that are selected differentially in two populations, although such comparisons between populations have been historically useful in identifying the action of natural selection. We have developed two fixed effects maximum likelihood methods: one for...

Over the years, many studies have attempted to establish a link between tobacco smoking and an increased risk of nasopharyngeal carcinoma (NPC), but their results have been inconsistent. To clarify this link, we first conducted a comprehensive meta-analysis to integrate the findings of epidemiologic studies from the last halfcentury. The methodology used for this study followed the checklist pr...

Background and Purpose—The factor V Leiden mutation is associated with ischemic stroke in children but not in adults. Whether it is associated with ischemic stroke in young adults, however, is uncertain. Methods—To address this issue, we performed a meta-analysis of 18 case-control studies of ischemic stroke in adults 50 years of age and younger published before June 2009. Results—Across all st...

We study panel data estimators based on a discretization of unobserved heterogeneity when individual heterogeneity is not necessarily discrete in the population. We focus on two-step grouped-fixed effects estimators, where individuals are classified into groups in a first step using kmeans clustering, and the model is estimated in a second step allowing for group-specific heterogeneity. We anal...

Over the years, many studies have attempted to establish a link between tobacco smoking and an increased risk of nasopharyngeal carcinoma (NPC), but their results have been inconsistent. To clarify this link, we first conducted a comprehensive meta-analysis to integrate the findings of epidemiologic studies from the last halfcentury. The methodology used for this study followed the checklist pr...

Background: Mass media campaigns are frequently used to influence the health behaviors of various populations. There are currently no quantitative meta-analyses of the effect of mass media campaigns on physical activity in adults. Methods: We searched six electronic databases from their inception to August 2012 and selected prospective studies that evaluated the effect of mass media campaigns o...

Objective To assess the evidence for a differential effect of positive prevention interventions among individuals infected and not infected with human immunodeficiency virus (HIV) in developing countries, and to assess the effectiveness of interventions targeted specifically at people living with HIV. Methods We conducted a systematic review and meta-analysis of papers on positive prevention be...

Much of the disagreement over whether households are adequately prepared for retirement reflects differences in assumptions regarding the extent to which consumption declines when the kids leave home. If consumption declines substantially when the kids leave home, as some life-cycle models of retirement saving assume, households need to achieve lower replacement rates in retirement and need to ...