In two-stage randomization trials subjects are first randomized to an initial treatment, and then if and when a response (or nonresponse) criterium is met, re-randomized to a second-stage treatment. When the primary outcome is a time to event, sample size calculation is challenging because the variances of common estimators depend in a complex manner on the joint distribution of primary time to...

INTRODUCTION Osteoarthritis (OA) is a major health problem and a leading cause of disability. The knee joint is commonly affected, resulting in pain and physical dysfunction. Exercise is considered the cornerstone of conservative management, yet meta-analyses indicate, at best, moderate effect sizes. Treatments that bolster the effects of exercise, such as transcranial direct current stimulatio...

INTRODUCTION The purpose of this article was to evaluate the quality of sample size calculation reports in published clinical trials in Journal of Endodontics and International Endodontic Journal in years 2000-1 and 2009-10. MATERIALS AND METHODS Articles fulfilling the inclusion criteria were collected. The criteria were: publication year, research design, types of control group, reporting s...

Accumulating evidence indicates high risk of bias in preclinical animal research, questioning the scientific validity and reproducibility of published research findings. Systematic reviews found low rates of reporting of measures against risks of bias in the published literature (e.g., randomization, blinding, sample size calculation) and a correlation between low reporting rates and inflated t...