August 29, 2013 Version 0.0.6 Date 2012-03-28 Title Power and sample size calculation for survival analysis of epidemiological studies Author Weiliang Qiu , Jorge Chavarro , Ross Lazarus , Bernard Rosner , Jing Ma . Maintainer Weiliang Qiu <stwxq@ch...

BACKGROUND Sample size planning for longitudinal data is crucial when designing mediation studies because sufficient statistical power is not only required in grant applications and peer-reviewed publications, but is essential to reliable research results. However, sample size determination is not straightforward for mediation analysis of longitudinal design. METHODS To facilitate planning th...

Shyness and loneliness both are very common in human being. Loneliness is often associated with a variety of personality characteristics which interfere with the formation of interpersonal relationship. In many studies it is found that shyness and loneliness are interrelated with each other. The present study was conducted on college students. The sample size consists of 60 college students (30...

One-sample and two-sample t-tests are commonly used in analyzing data from clinical trials in comparing mean responses from two drug products. During the planning stage of a clinical study, a crucial step is the sample size calculation, i.e., the determination of the number of subjects (patients) needed to achieve a desired power (e.g., 80%) for detecting a clinically meaningful difference in t...

BACKGROUND The current methodology for sample size calculations for stepped-wedge cluster randomised trials (SW-CRTs) is based on the assumption of equal cluster sizes. However, as is often the case in cluster randomised trials (CRTs), the clusters in SW-CRTs are likely to vary in size, which in other designs of CRT leads to a reduction in power. The effect of an imbalance in cluster size on th...

OBJECTIVES To assess quality of reporting of sample size calculation, ascertain accuracy of calculations, and determine the relevance of assumptions made when calculating sample size in randomised controlled trials. DESIGN Review. DATA SOURCES We searched MEDLINE for all primary reports of two arm parallel group randomised controlled trials of superiority with a single primary outcome publi...

In many clinical trials, longitudinal or repeated measures data is collected in order to monitor the patient’s progress over time towards a clinical end-point. One method of accounting for the two outcomes is by using joint modelling methods. However, little work has been done on sample size calculations for studies which use joint modelling of longitudinal and time-to-event data to establish t...

We study convergence properties of the resistance distance on random geometric graphs for increasing sample size. It turns out that the suitably scaled resistance distance between two fixed points converges to a non-trivial limit. However, this limit no longer takes into account global properties of the graph, as for example the cluster structure. Quite to the opposite, the limit distance funct...

OBJECTIVES To determine the smoking prevalence and to examine the determinants of smoking behaviour among male adolescents in Semarang, Indonesia. DESIGN A random sample of schools in Semarang (population 1.5 million) was obtained using a stratified sampling procedure (strata based on type of school and district). A total of 149 schools were selected (response rate 72%). Within the schools 18...

As data sets of related studies become more easily accessible, combining data sets of similar studies is often undertaken in practice to achieve a larger sample size and higher power. A major challenge arising from data integration pertains to data heterogeneity in terms of study population, study design, or study coordination. Ignoring such heterogeneity in data analysis may result in biased e...