			Home About us Contact

Statistical Considerations (statistical + consideration)

Distribution by Scientific Domains

Medical Sciences	40%

Selected Abstracts

Statistical consideration of the role of potential confounders on the association between immunological responses and disease

PARASITE IMMUNOLOGY, Issue 5 2008
J. TODD
No abstract is available for this article. [source]

An experimental study on the transformer coil leakage current

EUROPEAN TRANSACTIONS ON ELECTRICAL POWER, Issue 3 2006
Mohamed A. A. Wahab
This paper is concerned with the transformer coil dc leakage current under different conditions. These conditions include in-air, and in-oil leakage, currents with or without artificial coil deposits. In-oil leakage, currents are investigated when the coil is immersed in new or used transformer oil at different temperatures. The results showed that the leakage current increases with the increase in the applied voltage and oil temperatures. The rate of increase in leakage current with temperature depends on the transformer oil and coil conditions. The in-oil leakage currents are higher than those obtained in air. The leakage currents measured in used oil are higher than those resulted in new oil. Copper deposits cause higher values of leakage current than iron deposits for the same medium, applied voltage and temperature. Deposits increase the leakage current for different coil surrounding media. A linear model for the leakage current as a function of the applied voltage under different conditions has been found and its validity has been justified by statistical consideration. The parameters of this model account for various experimental conditions. Copyright © 2006 John Wiley & Sons, Ltd. [source]

Noninferiority and equivalence designs: Issues and implications for mental health research

JOURNAL OF TRAUMATIC STRESS, Issue 5 2008
Carolyn J. Greene
The terms noninferiority and equivalence are often used interchangeably to refer to trials in which the primary objective is to show that a novel intervention is as effective as the standard intervention. The use of these designs is becoming increasingly relevant to mental health research. Despite the fundamental importance of these designs, they are often poorly understood, improperly applied, and subsequently misinterpreted. In this article, the authors explain noninferiority and equivalence designs and key methodological and statistical considerations. Decision points in using these designs are discussed, such as choice of control condition, determination of the noninferiority margin, and calculation of sample size and power. With increasing utilization of these designs, it is critical that researchers understand the methodological issues, advantages, disadvantages, and related challenges. [source]

Assessing teratogenicity of antiretroviral drugs: monitoring and analysis plan of the Antiretroviral Pregnancy Registry,,

PHARMACOEPIDEMIOLOGY AND DRUG SAFETY, Issue 8 2004
Deborah L. Covington DrPH
Abstract This paper describes the Antiretroviral Pregnancy Registry's (APR) monitoring and analysis plan. APR is overseen by a committee of experts in obstetrics, pediatrics, teratology, infectious diseases, epidemiology and biostatistics from academia, government and the pharmaceutical industry. APR uses a prospective exposure-registration cohort design. Clinicians voluntarily register pregnant women with prenatal exposures to any antiretroviral therapy and provide fetal/neonatal outcomes. A birth defect is any birth outcome ,20 weeks gestation with a structural or chromosomal abnormality as determined by a geneticist. The prevalence is calculated by dividing the number of defects by the total number of live births and is compared to the prevalence in the CDC's population-based surveillance system. Additionally, first trimester exposures, in which organogenesis occurs, are compared with second/third trimester exposures. Statistical inference is based on exact methods for binomial proportions. Overall, a cohort of 200 exposed newborns is required to detect a doubling of risk, with 80% power and a Type I error rate of 5%. APR uses the Rule of Three: immediate review occurs once three specific defects are reported for a specific exposure. The likelihood of finding three specific defects in a cohort of ,600 by chance alone is less than 5% for all but the most common defects. To enhance the assurance of prompt, responsible, and appropriate action in the event of a potential signal, APR employs the strategy of ,threshold'. The threshold for action is determined by the extent of certainty about the cases, driven by statistical considerations and tempered by the specifics of the cases. Copyright © 2004 John Wiley & Sons, Ltd. [source]

Determination of ion track and shapes with damage simulations on the base of ellipsometric and backscattering spectrometric measurements

PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 5 2008
O. Polgár
Abstract On the base of geometrical and statistical considerations a damage simulator was created in order to determine the ion track-radius and -shape of ion-implantation caused damage in single-crystalline Si. Damage vs. dose curves calculated by spectroscopic ellipsometry (SE) and Rutherford backscattering/channeling spectrometry (RBS/C) measurements, using different doses of 100 keV Xe implantation, gave information about the damage profile in depth. Both methods are required, because of dose-dependent discrepancies of SE compared with RBS/C [Fried et al., Thin Solid Films 455/456, 404 (2004)]. Different kinds of damage models were investigated to calculate the ion track-radius and to describe the damages in depth and the shape of ion track. Comparing directly the simulated and the measured damage vs. dose curves, the damage function and the other simulation parameters were optimized and hence the ion track size and even the shape can be determined. The dose dependent mean size of the unchanged crystalline regions, obtained from the simulation was correlated with the complex dielectric functions, obtained from the SE analysis. The results clearly show the effect of decreasing size of the unchanged crystalline regions. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]