نتایج جستجو برای: sample size calculation
تعداد نتایج: 994380 فیلتر نتایج به سال:
Sample size calculation formulas for testing equality, noninferiority, superiority, and equivalence based on odds ratio were derived under both parallel and one-arm crossover designs. An example concerning the study of odds ratio between a test compound (treatment) and a standard therapy (control) for prevention of relapse in subjects with schizophrenia and schizoaffective disorder is presented...
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 Previous reviews have focussed on the rationale for employing the stepped wedge design (SWD), the areas of research to which the design has been applied and the general characteristics of the design. However these did not focus on the statistical methods nor addressed the appropriateness of sample size methods used.This was a review of the literature of the statistical methodology us...
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...
background and purpose: sample size and its determination is one of the most important problems in health researches. calculating sample size for prevalence studies is one of the common questions of sample size topics. minimum sample size with least complexity is desirable in order to achieve the basic goal of these studies. this study aims to compare two formulas of sample size calculation for...
Background Native T1 mapping is becoming established to help diagnose and monitor myocardial disease. The reproducibility of T1 mapping has not been well characterized, despite the important implications both for interpreting serial clinical studies, and for sample size calculation for surrogate endpoint in clinical trials. The SCMR consensus statement recommends measuring T1 in 2 imaging views...
The false discovery proportion FDP , the proportion of incorrect rejections among all rejections, is a direct measure of abundance of false positive findings in multiple testing. Many methods have been proposed to control FDP, but they are too conservative to be useful for power analysis. Study designs for controlling the mean of FDP, which is false discovery rate, have been commonly used. Howe...
BACKGROUND Although randomized clinical trials (RCTs) are considered the gold standard of evidence, their reporting is often suboptimal. Trial registries have the potential to contribute important methodologic information for critical appraisal of study results. METHODS AND FINDINGS The objective of the study was to evaluate the reporting of key methodologic study characteristics in trial reg...
In the clinical trial designing stage, trial statisticians need to provide a reference sample size for conducting the trial. In general, this task could be completed by forming the main research question into a statistical procedure and then implementing the published formulae or software, such as n-query and STATA, to make the calculation. When more complex statistical procedures are involved ...
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