نتایج جستجو برای: stratification

تعداد نتایج: 30687  

2016
Renfang Jiang Jianping Dong Yilin Dai

Backgrounds: Although many disease-associated common variants have been discovered through genome-wide association studies, much of the genetic effects of complex diseases have not been explained. Population-based association studies are vulnerable to population stratification. A possible solution is to use family-based tests. However, if tests only estimate the genetic effect from the within-f...

2016
Florence H. Yong Lu Tian Sheng Yu Tianxi Cai L. J. Wei

A common practice in predictive medicine is to use current study data to construct a stratification procedure, which groups subjects according to baseline information and forms stratum-specific prevention or intervention strategies. A desirable stratification scheme would not only have small intra-stratum variation but also have a clinically meaningful discriminatory capability. We show how to ...

Journal: :The international journal of biostatistics 2011
Brian L Egleston

Dr. Pearl invites researchers to justify their use of principal stratification. This comment explains how the use of principal stratification simplified a complex mediational problem encountered when evaluating a smoking cessation intervention's effect on reducing smoking withdrawal symptoms.

A. Bonis A. Sattarian J.B. Bouzillé M. Mohammad Esmaeili,

Carex divisa is a patrimonial rhizomatous species and acts as an important component of grazed wet permanent grassland on the French Atlantic coast. This study treated three storage regimes (wet-cold, dry-cold and dry-warm), burial in soil, fluctuating temperature and salinity on seed germination of C. divisa. The seeds were dormant at maturity. No seed germinated after 2 and 6 weeks of dry sto...

Behrang Sajadi Mehrdad Shirinbakhsh Nima Mirkhani

Many researchers have investigated how to increase the overall efficiency of solar-driven thermal systems. Several key parameters, such as collector efficiency and storage tank characteristics, may impose some constraints on the annual solar fraction (ASF) of such systems. In this paper, the behaviour of integrating the phase change material (PCM) in SDHW systems is modelled and optimized n...

2002
F. Jay Breidt Jean D. Opsomer

Post-stratification is frequently used to improve the precision of survey estimators when categorical auxiliary information is available from sources outside the survey. In natural resource surveys, such information is often obtained from remote sensing data, classified into categories. These stratification categories may be constructed based on models fitted to the sample data (“endogenous pos...

2012
Eric Arobone Sutanu Sarkar

Linear stability analysis is used to investigate instability mechanisms for a horizontally oriented hyperbolic tangent mixing layer with uniform stable stratification and coordinate system rotation about the vertical axis. The important parameters governing inviscid dynamics are maximum shear S, buoyancy frequency N, angular velocity of rotation Ω and characteristic shear thickness L. Growth ra...

2007
Mikko Peltoniemi Juha Heikkinen Raisa Mäkipää

Monitoring changes in soil C has recently received interest due to reporting under the Kyoto Protocol. Model-based approaches to estimate changes in soil C stocks exist, but they cannot fully replace repeated measurements. Measuring changes in soil C is laborious due to small expected changes and large spatial variation. Stratification of soil sampling allows the reduction of sample size withou...

2015
Hu Wang Zunqing Zheng Haifeng Liu Mingfa Yao

This paper presents a review on the combustion mode design with high efficiency and low emissions controlled by fuel reactivity and mixture stratification that have been conducted in the authors’ group, including the charge reactivity controlled homogeneous charge compression ignition (HCCI) combustion, stratification controlled premixed charge compression ignition combustion, and dual-fuel com...

2009
Sara M Sarasua Julianne S Collins Dhelia M Williamson Glen A Satten Andrew S Allen

The North American Rheumatoid Arthritis Consortium case-control study collected case participants across the United States and control participants from New York. More than 500,000 single-nucleotide polymorphisms (SNPs) were genotyped in the sample of 2000 cases and controls. Careful adjustment for the confounding effect of population stratification must be conducted when analyzing these data; ...

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