BACKGROUND: In epidemiologic studies researchers are often interested in detecting confounding (when a third variable is both associated with and affects associations between the outcome and predictors). Confounder detection methods often compare regression coefficients obtained from "crude" models that exclude the possible confounder(s) and "adjusted" models that include the variable(s). One s...

This paper investigates a change-point estimation problem in the context of high-dimensional Markov random field models. Change-points represent a key feature in many dynamically evolving network structures. The change-point estimate is obtained by maximizing a profile penalized pseudo-likelihood function under a sparsity assumption. We also derive a tight bound for the estimate, up to a logari...

PURPOSE To review microbial contamination rates about preparation of individual and batch doses using aseptic techniques within pharmaceutical (controlled) and clinical (ward and theatre) environments. METHODS Systematic review, involving amalgamation of data using a random effect model and metaanalysis. RESULTS A total of 19 studies from 17 reports (7277 doses), mostly single arm studies, ...

The ability to mentalize has been marked as an important cognitive mechanism enabling belief in supernatural agents. In five studies we cross-culturally investigated the relationship between mentalizing and belief in supernatural agents with large sample sizes (over 67,000 participants in total) and different operationalizations of mentalizing. The relative importance of mentalizing for endorsi...

Studies of the effects of patch size and isolation on plant species density have yielded contrasting results. However, much of the available evidence comes from relatively recent anthropogenic forest fragments which have not reached equilibrium between extinction and immigration. This is a critical issue because the theory clearly states that only when equilibrium has been reached can the numbe...

Interactions measured on the additive scale are more relevant than multiplicative interaction for assessing public health importance and also more closely related to notions of mechanistic synergism. Most work on sample size and power calculations for interaction have focused on the multiplicative scale. Here we derive analytic expressions for sample size and power calculations for interactions...

The effects of sample size on fitting length distribution of wood particles used for manufacturing wood-based composites were investigated. A simulation study was conducted to evaluate the variations of the first four sample moments and the ability of the sample distributions to characterize the population represented by the original data. Results showed that a sample size of 2000 was deemed ne...

We describe and compare four different methods for estimating sample size and power, when the primary outcome of the study is a Health Related Quality of Life (HRQoL) measure. These methods are: 1. assuming a Normal distribution and comparing two means; 2. using a non-parametric method; 3. Whitehead's method based on the proportional odds model; 4. the bootstrap. We illustrate the various metho...

Sequential tests outperform fixed sample size tests by requiring fewer samples on average to achieve the same level of error performance. The Sequential Probability Ratio Test (SPRT) has been suggested by Wald [1] for sequential binary hypothesis testing problems. SPRT recursively calculates the likelihood of an observed data stream and requires this likelihood to be stored in memory between sa...

In this paper, a Bayesian approach is developed for simultaneously comparing multiple experimental treatments with a common control treatment in an exploratory clinical trial. The sample size is set to ensure that, at the end of the study, there will be at least one treatment for which the investigators have a strong belief that it is better than control, or else they have a strong belief that ...