The potential for bias in principal causal effect estimation when treatment received depends on a key covariate

Motivated by a potential-outcomes perspective, the idea of principal stratification has been widely recognized for its relevance in settings susceptible to posttreatment selection bias such as randomized clinical trials where treatment received can differ from treatment assigned. In one such setting, we address subtleties involved in inference for causal effects when using a key covariate to predict membership in latent principal strata. We show that when treatment received can differ from treatment assigned in both study arms, incorporating a stratum-predictive covariate can make estimates of the "complier average causal effect" (CACE) derive from observations in the two treatment arms with different covariate distributions. Adopting a Bayesian perspective and using Markov chain Monte Carlo for computation, we develop posterior checks that characterize the extent to which incorporating the pretreatment covariate endangers estimation of the CACE. We apply the method to analyze a clinical trial comparing two treatments for jaw fractures in which the study protocol allowed surgeons to overrule both possible randomized treatment assignments based on their clinical judgment and the data contained a key covariate (injury severity) predictive of treatment received.Comment: Published in at http://dx.doi.org/10.1214/11-AOAS477 the Annals of Applied Statistics (http://www.imstat.org/aoas/) by the Institute of Mathematical Statistics (http://www.imstat.org

Common internal parasites of cattle (1993)

Although there are many species of worm parasites harbored in the gastrointestinal and respiratory tracts of cattle, only a few target species are clinically and economically important. These include the brown stomach worm Ostertagia the coccidia Eimeria bovis and the lungworm Dictyocaulus. These are of great significance throughout the United States and worldwide, with Ostertagia considered the single most important parasite of cattle. And this is true for native Missouri cattle as well as for cattle imported into Missouri

Handheld Technology: Impact On Student Learning

The author in this project presents research on: (a) handheld technology in the classroom, (b) challenges of handheld technology, (c) pedagogical benefits of handheld technology in the classroom, and (d) methods of technology implementation. The utilization of handheld technology in the classroom improves students\u27 learning of concepts and skills. A major concern of the educator is that, with the use of technology, students will bypass the bridge to genuine understanding, and instead obtain a relatively effortless solution to standard problems through technology aids, while they present the appearance of mastery of a concept. However, research indicates that technology, when implemented effectively, expands student learning and alleviates teachers\u27 concerns about whether or not the technology gives a false impression of the students having mastered material. This information on handheld technology was dispersed to math and science educators through a Power Point presentation. The images of the Power Point presentation as well as the activities completed by the educators during the inservice are included in this project

Avian Community Response to Seasonal and Successional Changes

2012 S.C. Water Resources Conference - Exploring Opportunities for Collaborative Water Research, Policy and Managemen