Model Uncertainty and Model Averaging in the Estimation of Infectious Doses for Microbial Pathogens

Food‐borne infection is caused by intake of foods or beverages contaminated with microbial pathogens. Dose‐response modeling is used to estimate exposure levels of pathogens associated with specific risks of infection or illness. When a single dose‐response model is used and confidence limits on infectious doses are calculated, only data uncertainty is captured. We propose a method to estimate the lower confidence limit on an infectious dose by including model uncertainty and separating it from data uncertainty. The infectious dose is estimated by a weighted average of effective dose estimates from a set of dose‐response models via a Kullback information criterion. The confidence interval for the infectious dose is constructed by the delta method, where data uncertainty is addressed by a bootstrap method. To evaluate the actual coverage probabilities of the lower confidence limit, a Monte Carlo simulation study is conducted under sublinear, linear, and superlinear dose‐response shapes that can be commonly found in real data sets. Our model‐averaging method achieves coverage close to nominal in almost all cases, thus providing a useful and efficient tool for accurate calculation of lower confidence limits on infectious doses.     

Revised Historical Viewpoints

The author describes the use of literature circles in a social studies methods course for elementary preservice teachers and analyzes their effectiveness in teaching powerful social studies ideas. Literature circles encourage students to take more of a leadership role in the classroom, expect their active involvement, and challenge them to think more deeply about social studies content within texts. Students can compare different perspectives on the same historical event, such as the encounter between Columbus and the Taino, and reasons for including and omitting important ideas. Students can also note similarities and differences among cultures and current and historical events through literature circle discussions. However, teachers must carefully select texts which focus on powerful social studies ideas, emphasize the goal of thoughtful discussions when introducing literature circles, and be ready to raise significant issues ignored in the literature circle discussions during follow-up class discussions.     

Some adjusted orthogonal,variance balanced,multidimensional block designs

A multidimensional block design (MBD) is an experimental design with d > 1 blocking criteria geometrically represented as a d-dimensional lattice with treatment varieties assigned to some or all nodes of the lattice. Intrablock analysis of variance tables for some special classes of two- and three-dimensional block designs with some empty nodes are given. Design plans and efficiencies for 31 two-dimensional designs, each universally optimal in defined classes of designs, and 7 three-dimensional designs, each nearly optimal in defined classes of designs, are listed in the appendices. A need for such designs is apparent when the blocking criteria are implemented successively and empty nodes do not represent wasted experimental units.     

Representative Designs and Their Challenges

Abstract

In this article, the authors explore three research designs common to college health investigations: survey, epidemiologic, and experimental. They identify the varieties of research questions addressed by these designs and note examples from clinical nursing/medicine, mental health, and health education topics. In addition, the authors summarize the unique challenges encountered in each of these designs, including issues of sample selection, adequate measurement, and control.