نتایج جستجو برای: sample size calculation
تعداد نتایج: 994380 فیلتر نتایج به سال:
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...
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...
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...
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...
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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 ...
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...
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 ...
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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