Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
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Showing 1 to 20 of 2533 for “"Sample Size"”.
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Methods of sample size calculation for clinical trials
Sample size calculations should be an important part of the design of a trial, but are researchers choosing sensible trial sizes? This thesis looks at ways of determining appropriate sample sizes for Normal, binary and ordinal data. The inadequacies of existing sample size and power calculation …
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Power and Sample Size for Three-Level Cluster Designs
… intervention effect. The assessment of power and sample size in such studies is often faced with many challenges due to several methodological difficulties. While studies on power and sample size for cluster designs with one and two levels are abundant, the evaluation of required sample size for …
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Extending Sample Size Calculation for the Cox Proportional Hazards Model
… lymphoma disease. The popularly used sample size formula derived under the Cox proportional hazards (PH) model may not be proper to design a survival trial with a cure fraction, since the PH model assumption may be violated. To account for a cure fraction, the PH cure model is widely …
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Topics in Bayesian sample size determination and Bayesian model selection.
… The first topic is related to Bayesian sample size determination with a misclassified prevalence variable when two possibly dependent diagnostic tests are used for estimation. After accounting for the dependence structure, the required sample size will be larger than that assuming …
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Optimal round and sample-size complexity for partitioning in parallel sorting
Submission published under a 24 month embargo labeled 'Closed Access', the embargo will last until 2024-05-01
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An Evaluation of the Small Sample Size Properties of Tests of Localization
… there is little information regarding the small sample size properties of the tests. Often, agglomeration researchers choose tests without knowledge of their properties and relative performance. This paper evaluates the small sample size properties of discrete tests of localization using Monte …
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The Effect of Sample Size on Rapid Bioassessment Scores and Management Efficiency
… of 200 macro invertebrates as the standard subsample size. This number has been argued to be too small to provide accurate estimates on the richness of macro invertebrate communities and is believed to give misleading information pertaining to stream health. In this study, I used data collected …
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Estimation of Variation For High-throughput Molecular Biological Experiments With Small Sample Size
… experiments often involve a small number of samples due to the limitation of cost and time. In such cases, the stochastic information may dominate the outcome of an experiment because there may not be enough samples to present the true biological information. It is challenging to distinguish …
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Bayesian sample-size determination and adaptive design for clinical trials with Poisson outcomes.
… researchers often need to determine the smallest sample size that provides accurate inferences for a parameter of interest or need to adaptive design elements during the course of the trial based on information that is initially unknown. Although most experimenters have employed frequentist …
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Some considerations of an optimum sample size for a one-stage sampling procedure
… purpose of this work is to discover an optimum sample size to be used for deciding between two methods (populations) to choose for future production. The procedure involves the formulation of a loss function, expressing the expected loss due to choosing the population with the small mean, as a …
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Challenges faced by IRB Approved Studies due to Sample Size Shortfalls and Low Patient Accrual
… participants. However, continued issues with sample size short falls and low patient accruals remain some of the greatest challenges IRB-approved studies face. This thesis undertakes comprehensive evaluation of these challenges, examine their complexities and ethical implications. Drawing on a …
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Topics in Bayesian models with ordered parameters : response misclassification, covariate misclassification, and sample size determination.
… hypotheses (Hoijtink, 2012) and perform sample size determination for this problem using the two priors approach of Brutti et al. (2008).
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Monetary Unit Acceptance Sampling: Sequential and Fixed Sample Size Plans for Substantive Tests in Auditing
… by nominal risks. Both sequential and fixed sample size plans are developed, and, for these plans, both classical and Bayesian models are proposed. MUAS is derived from physical unit acceptance sampling and thereby provides a conceptual unification of statistical compliance and substantive …
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Sample Size Formulas For Estimating Areas Under the Receiver Operating Characteristic Curves With Precision and Assurance
… new test, it is important to determine a minimum sample size required to achieve a prespecified precision of estimating AUC. However, conventional sample size formulas do not consider the probability of achieving a prespecified precision, resulting in underestimation of sample sizes. To …
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The Impact of Sample Size, Prevalence, Estimation Method and Other Factors When Estimating Multilevel Logistic Models
<p>Sample size guidelines for binary outcome multilevel models are rare, despite well-established rules-of-thumb for continuous outcome multilevel models. When considering requisite sample sizes for designing studies utilizing such models, applied practitioners would be remiss in failing to take …
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Linear viscoelastic characteristics of Michigan asphalt mixtures and the effect of sample size on material properties
The Mechanistic-Empirical Pavement Design Guide (M-E PDG) is becoming the state-of-the-practice in both newly constructed and rehabilitated pavement designs. A number of different material inputs are required by the M-E PDG, and accurate measurement of these inputs is crucial for the accuracy of …
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Sample Size Calculation Based on the Semiparametric Analysis of Short-term and Long-term Hazard Ratios
We derive sample size formulae for survival data with non-proportional hazard functions under both fixed and contiguous alternatives. Sample size determination has been widely discussed in literature for studies with failure-time endpoints. Many researchers have developed methods with the …
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