• Journal of Radiation Protection and Research
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• v.41 no.4
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• pp.402-408
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• 2016

Background: Ascertainment bias are common in epidemiologic studies to assess the association between thyroid cancer risk and living near nuclear power plants because many thyroid cancers are diagnosed by chance through health examination. We surveyed the ultra sonography (USG) examination history and conducted thyroid and breast USG in residents living near nuclear power plants. Materials and Methods: The study population comprised 2,421 residents living near nuclear power plants in Korea. Information on demographic characteristics, including diagnostic examination history, was collected by interview using questionnaires. USG examination was conducted to evaluate the presence of thyroid nodules and breast lesion. Study participants were divided into 3 groups according to the distance of their respective villages from a nuclear power plant. The proportions of USG examination history and prevalence of thyroid nodules and breast lesions were compared between groups. Results and Discussion: Examination histories of thyroid USG were 23.1%, 13.7%, and 10.5% in men and 31.3%, 26.7%, 18.3% in women in the short, intermediate, and long distance groups, respectively. There were significant inverse associations between thyroid USG history and the distance from nuclear power plants (P for trend = 0.001 for men and 0.017 for women). However, there was no association between the distance of villages from nuclear power plants and prevalence of thyroid nodules. Conclusion: Our results suggest that there may be an ascertainment bias in population-based studies examining the harmful effects of NPPs examination and researchers should pay attention to ascertainment bias resulted from differential health examination. Correction for ascertainment bias, active follow-up and examination for all study population to remove differential health examination is needed.

• Communications for Statistical Applications and Methods
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• v.26 no.2
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• pp.103-129
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• 2019

The main goal of a case-control study is to learn the association between various risk factors and a primary outcome (e.g., disease status). Particularly recently, it is also quite common to perform secondary analyses of the case-control data in order to understand certain associations between the risk factors of the primary outcome. It has been repeatedly documented with case-control data, association studies of the risk factors that ignore the case-control sampling scheme can produce highly biased estimates of the population effects. In this article, we review the issues of the naive secondary analyses that do not account for the biased sampling scheme, and also the various methods that have been proposed to account for the case-control ascertainment. We additionally compare the results of many of the discussed methods in an example examining the association of a particular genetic variant with smoking behavior, where the data were obtained from a lung cancer case-control study.

• Korea and Global Affairs
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• v.1 no.2
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• pp.5-32
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• 2017

5.18 Gwangju Democratization Movement was approved as a legal democratization movement by president Kim Young Sam in May 1993 and was approved as a global recording inheritance by UNESCO in May 2011 for the honor of Gwangju citizens to be restored. However, assessment on this until today after 35 years of occurrence is not nationally unified and the mind of Gwangju maybe only remembered as pride by Gwangju. There are several factors of this continuing situation but this researcher thinks the biggest factor is that professionals reanalyzing the truth ascertainment fitting spirit of the times who are in charge of citizen education are intensively distributed in Jeolla-do and Seoul. Moreover, the journal unlikely assessing 5.18 have enemies in the assailant area during activity that unity is not taking place with divided assessments and trapped in Honam. This study judges that the reason the meaning of 5.18 is trapped in Honam and not nationally unified is because of the limit of "adversary system." Especially researchers who should analyze and explain this incident in a objective views are bias distributed (Gwangju Jeolla-do> Seoul>Gyeongnam) in hometown areas that the possibility of 5.18 meaning not being unified was focused. Academic research studies, journal writers, and publication locations are divided in this study to reveal they are bias distributed and reveal that there is possibility that this biased distribution of researches are becoming obstacles in overcoming regionality.