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...

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...

One of the objectives of the research done in statistical process control is to obtain control charts that show few false alarms but, at the same time, are able to detect quickly the shifts in the distribution of the quality variables employed to monitor a productive process. In this paper the synthetic-T control chart is developed, which consists of the simultaneous use of a CRL chart and a Ho...

optimum sample size is an essential component of any research. the main purpose of the sample size calculation is to determine the enough number of units needed to detect the unknown clinical parameters or the treatment effects or the association after data gathering. it is not uncommon for studies to be underpowered and failing to detect the existed treatment effects due to inadequate sample s...

this paper addresses the design of control charts for both variable ( x chart) andattribute (u and c charts) quality characteristics, when there is uncertainty about the processparameters or sample data. derived control charts are more flexible than the strict crisp case, dueto the ability of encompassing the effects of vagueness in form of the degree of expert’spresumption. we extend the use o...

INTRODUCTION The objective was to review the effect of Internet-based continuing medical education (CME) interventions on physician performance and health care outcomes. METHODS Data sources included searches of MEDLINE (1966 to January 2004), CINAHL (1982 to December 2003), ACP Journal Club (1991 to July/August 2003), and the Cochrane Database of Systematic Reviews (third quarter, 2003). Stu...

background: general practitioners are the first who visit burn patients and they first calculate burn size and required fluid for the patient. error in calculation can be disastrous. the purpose of this study is to compare four methods of estimating burn size to teach students. methods: this is a descriptive-analytic study on 37 medical students. four methods of estimating burn percentage was t...