• 한국항공운항학회지
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• 제26권4호
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• pp.64-75
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• 2018

A status of air traffic controller is a government officer and air traffic controllers who work at airport are divided by duty rating and work experience. Abiding by law, rules and regulation, air traffic controllers are working together based on mutual trust. This paper's theoretical background is based on cultural bias theory. The theory divide people group into four groups according to cultural bias such as fatalism, hierarchy, individualism and egalitarianism. A research model was designed how such four cultural bias could affect air traffic controller's risk response in case of emergency or abnormal situation during their work. Depend on empirical research, it was found that air traffic controllers perceived they had been more biased to fatalism than hierarchy. The characteristics of fatalism group are as follows: first of all, they follow rigid rules and regulation. However, they have less self-efficacy compared to other government officers. According to structural equation model, air traffic controller's fatalism had a significant negative effect on organizational royalty. Their royalty, however, had a very significant positive effect on planning response and immediate response.

• 대한간호학회지
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• 제42권1호
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• pp.48-55
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• 2012

Purpose: The aim of this study was to compare statistical methods to control response bias in nursing activity surveys. Methods: Data were collected at a medical unit of a general hospital. The number of nursing activities and consumed activity time were measured using self-report questionnaires. Descriptive statistics were used to identify general characteristics of the units. Average, Z-standardization, gamma regression, finite mixture model, and stochastic frontier model were adopted to estimate true activity time controlling for response bias. Results: The nursing activity time data were highly skewed and had non-normal distributions. Among the 4 different methods, only gamma regression and stochastic frontier model controlled response bias effectively and the estimated total nursing activity time did not exceeded total work time. However, in gamma regression, estimated total nursing activity time was too small to use in real clinical settings. Thus stochastic frontier model was the most appropriate method to control response bias when compared with the other methods. Conclusion: According to these results, we recommend the use of a stochastic frontier model to estimate true nursing activity time when using self-report surveys.

• 응용통계연구
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• 제26권3호
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• pp.375-387
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• 2013

통계조사에서 단위 무응답은 표본크기를 축소시켜 추정값의 효율을 떨어뜨릴 뿐만 아니라, 주요 관심변수에 대해 응답자와 무응답자간의 차이가 존재하는 경우 무응답 편향(bias)을 발생시키는 요인으로 일반적으로 가중값 조정방법을 이용하여 보정한다. 대부분의 조사에서 무응답 표본에 대한 정보를 얻는 것은 현실적으로 매우 어려우며, 무응답으로 인한 추정값의 편향 정도를 파악하는 것 또한 쉽지 않다. 통계청에서는 2010년, 2011년 가구패널조사인 가계 금융조사를 실시하였다. 2010년 1차 웨이브는 1만 가구에 대해 모두 응답한 정보를 가지고 있으며, 2011년 2차 웨이브에는 부재, 거부 등으로 인한 무응답 표본(약 10%)이 존재한다. 본 연구에서는 2차 웨이브의 무응답 표본들을 무응답 성향이 강한 표본으로 가정하고 1차 웨이브에서 무응답가구로 분류한 후 무응답 가구의 특성과 무응답 편향정도 및 무응답 조정 효과를 분석하였다.

• Journal of the Korean Statistical Society
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• 제24권1호
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• pp.31-44
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• 1995

In fitting a model, there always exists a discrepancy between the fitted model and the true functional relationship. In measuring this discrepancy, Box and Drapper (1959) used the criterion dividing the discrepancy into two parts which are the bias error part and the variance error one in single response case. In this paper, an optimum design which makes these two types of errors as small as possible is found by extending the Box and Drapper criterion to multiple response situation. Especially, a design is found to meat rotatability conditions when we fit a quadratic model to each response fearing cubic bias. Using the central composite design, an application of general results to a specific case is shown to help understanding the material.

• 전기학회논문지
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• 제64권7호
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• pp.978-983
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• 2015

This paper presents Frequency Bias setting for the adequate AGC(Automatic Generator Control) operation based on the frequency response of power system in Korea. AGC frequency control recovers the frequency up to 60Hz following a primary control when the frequency suddenly drops due to a fault in power system. AGC can compensate an appropriate amount of generation by calculating ACE(Are Control Error) from the frequency deviation with the AGC frequency bias set from the actual frequency response in power systems. An appropriateness of the proposed AGC bias setting is verified through case studies employing the simulation model.

• 응용통계연구
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• 제23권3호
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• pp.533-543
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• 2010

직접면접으로 민감한 질문을 할때 발생하는 무응답이나 거짓응답의 문제를 개선하고자 Warner (1965)가 최초로 제안한 확률화응답모형에 관한 연구는 이후 많은 연구자들에 의해 개선, 발전되어 오고 있다. 본 연구에서 표본은 층화임의복원추출법에 의해 추출되었으며, 표본배분은 최적배분법에 의해 배분되었다. 한편, Kim과 Elam (2005)의 2단계 층화확률화응답모형을 확장한 3단계 층화확률화응답모형을 사용하였다. Kim과 Elam (2005)의 2단계 층화확률화응답모형과 상대효율을 비교한 결과 본 논문에서 제시한 3단계 층화확률화모형의 효율성이 상대적으로 높다는 결과가 도출되었다. 그러나 2단계확률화응답모형을 3단계로 확장함으로써 상대적으로 효율성은 증대되지만 반대로 조사과정의 어려움이 예상된다.

• 대한산업공학회지
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• 제38권1호
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• pp.25-30
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• 2012

Desirability approaches have been proposed to find an optimum of multiple response problem. The existing desirability approaches use either of mean or min of individual desirability in aggregation of multiple responses. However, in order to find an optimum having high mean and low dispersion among individual desirability, the dispersion needs to be simultaneously considered with its mean. This study proposes bias and variance (BV) method which aggregates bias (ideal target-mean) and variance of individual desirability in multiple response optimization. The proposed BV method was applied to an example to evaluate its usefulness by comparing with existing methods. Evaluation results showed that the solution of BV method was a fairly good compared with DS (Derringer and Suich, 1980) and KL (Kim and Lin, 2000) methods. The BV method can be utilized to multiple response surface problems when decision makers want to find an optimum having high mean and low variance among responses.

• Safety and Health at Work
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• 제12권2호
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• pp.174-183
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• 2021

Background: Toluene diisocyanate (TDI) is a highly reactive chemical that causes sensitization and has also been associated with increased lung cancer. A risk assessment was conducted based on occupational epidemiologic estimates for several health outcomes. Methods: Exposure and outcome details were extracted from published studies and a NIOSH Health Hazard Evaluation for new onset asthma, pulmonary function measurements, symptom prevalence, and mortality from lung cancer and respiratory disease. Summary exposure-response estimates were calculated taking into account relative precision and possible survivor selection effects. Attributable incidence of sensitization was estimated as were annual proportional losses of pulmonary function. Excess lifetime risks and benchmark doses were calculated. Results: Respiratory outcomes exhibited strong survivor bias. Asthma/sensitization exposure response decreased with increasing facility-average TDI air concentration as did TDI-associated pulmonary impairment. In a mortality cohort where mean employment duration was less than 1 year, survivor bias pre-empted estimation of lung cancer and respiratory disease exposure response. Conclusion: Controlling for survivor bias and assuming a linear dose-response with facility-average TDI concentrations, excess lifetime risks exceeding one per thousand occurred at about 2 ppt TDI for sensitization and respiratory impairment. Under alternate assumptions regarding stationary and cumulative effects, one per thousand excess risks were estimated at TDI concentrations of 10 - 30 ppt. The unexplained reported excess mortality from lung cancer and other lung diseases, if attributable to TDI or associated emissions, could represent a lifetime risk comparable to that of sensitization.

• 응용통계연구
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• 제33권4호
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• pp.409-420
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• 2020

사업체조사에서는 흔히 수정절사법이 사용되며 이 방법을 사용함으로써 표본의 수를 줄이면서도 추정의 정확성을 향상 시킬 수 있다. 그러나 전수층의 무응답률은 크게 높아지고 있으며 예비표본을 이용한 표본대체가 불가능하기 때문에 전수층에서 발생한 무응답은 추정의 정확성을 크게 떨어뜨리고 있다. 특히 무응답이 관심변수에 영향을 받는 경우에는 편향이 발생할 가능성이 매우 높기 때문에 이를 적절히 처리하는 것은 매우 중요하다. 본 연구에서는 전수층에서 발생한 무응답을 적절히 처리하는 방법의 하나로 편향보정 추정법을 제안하였다. 특히 Chung과 Shin(2020)에서 제안한 편향보정 추정량을 전수층 편향보정에 적용하였으며 전수층이라는 특수한 경우에 맞는 새로운 추정 방법을 제안하였다. 또한 모의실험을 통해 제안된 방법의 우수성을 살펴보았으며 실제 자료 분석을 실시하여 본 논문에서 제안한 방법의 우수성을 확인하였다.

• Communications for Statistical Applications and Methods
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• 제29권2호
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• pp.263-275
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• 2022

Use of appropriate technique for non-response occurring in sample survey improves the accuracy of the estimation. Many studies have been conducted for handling non-ignorable non-response and commonly the response probability is estimated using the propensity score method. Recently, post-stratification method to obtain the response probability proposed by Chung and Shin (2017) reduces the effect of bias and gives a good performance in terms of the MSE. In this study, we propose a new response probability estimation method by combining the propensity score adjustment method using the logistic regression model with post-stratification method used in Chung and Shin (2017). The superiority of the proposed method is confirmed through simulation.