BACKGROUND In this article, we discuss the purpose of sample size calculation in clinical trials, the need for it, and the methods by which it is accomplished. Study samples that are either too small or too large are unacceptable, for clinical, methodological, and ethical reasons. The physicians participating in clinical trials should be directly involved in sample size planning, because their ...

BACKGROUND Children with attention deficit hyperactivity disorder (ADHD) are hyperactive and impulsive, cannot maintain attention, and have difficulties with social interactions. Medical treatment may alleviate symptoms of ADHD, but seldom solves difficulties with social interactions. Social-skills training may benefit ADHD children in their social interactions. We want to examine the effects o...

BACKGROUND In healthcare research, outcomes with skewed probability distributions are common. Sample size calculations for such outcomes are typically based on estimates on a transformed scale (e.g. log) which may sometimes be difficult to obtain. In contrast, estimates of median and variance on the untransformed scale are generally easier to pre-specify. The aim of this paper is to describe ho...

BACKGROUND A trial was commissioned to evaluate the effectiveness of larval therapy to debride and heal sloughy and necrotic venous leg ulcers. Larval therapy in the trial was to be delivered in either loose or bagged form. Researchers were concerned that resistance to larval therapy may threaten the feasibility of the trial. Additionally there was concern that the use of larval therapy may req...

BACKGROUND In South Africa the estimated incidence of all forms of tuberculosis (TB) for 2008 was 960/100000. It was reported that all South Africans lived in districts with Directly Observed Therapy, Short-course. However, the 2011 WHO report indicated South Africa as the only country in the world where the TB incidence is still rising. AIMS To report the results of a TB prevalence survey an...

BACKGROUND Stepped-wedge cluster randomised trials (SW-CRT) are increasingly being used in health policy and services research, but unless they are conducted and reported to the highest methodological standards, they are unlikely to be useful to decision-makers. Sample size calculations for these designs require allowance for clustering, time effects and repeated measures. METHODS We carried ...

BACKGROUND The use of cluster randomized trials (CRTs) is increasing, along with the variety in their design and analysis. The simplest approach for their sample size calculation is to calculate the sample size assuming individual randomization and inflate this by a design effect to account for randomization by cluster. The assumptions of a simple design effect may not always be met; alternativ...

CONTEXT Noninferiority and equivalence trials aim to show that the experimental treatment is not clinically worse than (noninferior) or clinically similar to (equivalent) a control active treatment. These study objectives imply particular planning and analysis. OBJECTIVE To assess the methodologic quality of reports of randomized controlled trials of noninferiority and equivalence. DESIGN W...

In clinical research, in addition to continuous responses, primary clinical endpoints for assessment of efficacy and safety of a drug product under investigation could be binary responses. For example, in cancer trials, patients’ clinical reaction to the treatment is often classified as response (e.g., complete response or partial response) or nonresponse. Based on these binary responses, the p...

OBJECTIVE To establish the reporting quality of trials published in leading nursing journals and investigate associations between CONSORT Statement or trial registration endorsment and reporting of design elements. METHODS The top 15 nursing journals were searched using Medline for randomised controlled trials published in 2012. Journals were categorised as CONSORT and trial registration prom...