نتایج جستجو برای: sample size calculation

تعداد نتایج: 994380  

حقدوست, علی اکبر,

Sample size estimation is one of the crucial issues in the research methodology in medical sciences. It is an important issue for not only researchers but also readers of medical papers their frequent questions show how much they need to simple but accurate information. This paper presents the basic concepts of sample size calculation, and simplifies complicated issues using concrete example...

بانشی, محمد رضا, حقدوست, علی اکبر, مرزبان, مریم,

In the previous paper, the basic concepts of sample size calculation were presented. This paper explores main post-calculation adjustments of the sample size calculation in special circumstances such as multiple group comparisons, unbalanced studies (with unequal number of subjects in different groups) sample size correction for missing data, and adjustment for finite population size. In additi...

Journal: :Briefings in bioinformatics 2015
Elise Billoir Vincent Navratil Benjamin J. Blaise

The number of samples needed to identify significant effects is a key question in biomedical studies, with consequences on experimental designs, costs and potential discoveries. In metabolic phenotyping studies, sample size determination remains a complex step. This is due particularly to the multiple hypothesis-testing framework and the top-down hypothesis-free approach, with no a priori known...

2013
Mohamad Amin Pourhoseingholi Mohsen Vahedi Mitra Rahimzadeh

Optimum sample size is an essential component of any research. The main purpose of the sample size calculation is to determine the number of samples needed to detect significant changes in clinical parameters, treatment effects or associations after data gathering. It is not uncommon for studies to be underpowered and thereby fail to detect the existing treatment effects due to inadequate sampl...

2009
Nick Fox Amanda Hunn Nigel Mathers

This Resource Pack may be freely photocopied and distributed for the benefit of researchers. However it is the copyright of The NIHR RDS EM / YH and the authors and as such, no part of the content may be altered without the prior permission in writing, of the Copyright owner.

2007
V. Kasiulevičius V. Šapoka R. Filipavičiūtė

Sample-size determination is often an important step in planning an epidemiological study. There are several approaches to determining sample size. It depends on the type of the study. Descriptive, observational and randomized controlled studies have different formulas to calculate sample size. In this article, we discuss the formulas that can help to estimate sample size in an epidemiological ...

2008
Rajendra Kadel

Mediation analysis is used to review the comparative change in the amount of strength of association of the primary predictor with the outcome after adjustment for the mediator. Mediation models are very widely used in social sciences and biomedical sciences. Before conducting mediation studies, researchers want to know the sample size (i.e. number of subjects) required for achieving the adequa...

2006
HANSHENG WANG

In practice, the variabilities of responses involved in clinical research can be roughly divided into three categories. They are, namely, intra-subject, inter-subject, and total variabilities (1). More specifically, the intrasubject variability is the variability observed by repeated measurements on the same subject under exactly the same experiment conditions. This type of variability is very ...

Journal: :JPMA. The Journal of the Pakistan Medical Association 2012
Syed Asad Ali

پایان نامه :وزارت علوم، تحقیقات و فناوری - دانشگاه صنعتی اصفهان - دانشکده ریاضی 1390

the main objective in sampling is to select a sample from a population in order to estimate some unknown population parameter, usually a total or a mean of some interesting variable. a simple way to take a sample of size n is to let all the possible samples have the same probability of being selected. this is called simple random sampling and then all units have the same probability of being ch...

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