• Journal of the Korean Statistical Society
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• 제25권2호
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• pp.205-216
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• 1996

The bootstrap calibration method for empirical likelihood is considered to make a confidence region for the regression coefficients. Asymptotic properties are studied regarding the coverage probability. Small sample simulation results reveal that the bootstrap calibration works quite well.

• 한국조사연구학회:학술대회논문집
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• 한국조사연구학회 2001년도 추계학술대회 발표논문집
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• pp.77-85
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• 2001

무응답 상황하에서 보정 추정량에 대해 관심변수와 강한 상관계수를 가진 보조정보의 수준에 따라 모집단 총합에 대한 추정량과 분산추정량을 붓스트랩 방법을 이용해서 구했다. 이때 존재하는 보조정보의 수준이 표본인 경우와 모집단인 경우로 나누어 모집단 총합에 대한 보정 추정량(calibration estimator)을 구하고, 그에 따른 붓스트랩 분산 추정량을 도출하였다. 또한 테일러 분산 추정량, 잭나이프 분산 추정량과 붓스트램 분산 추정량의 효율성을 모의 실험을 통해 비교해 보았다.

• 응용통계연구
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• 제19권3호
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• pp.535-544
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• 2006

분산 성분 모형 하에서 분산 성분들의 함수에 대한 통계적인 추론, 특히 소표본 하에서의 신뢰구간에 대한 방법들은 오랜 기간에 걸쳐서 여러 가지 방법들이 개발되어져 왔다. 그 대표적인 방법이 Graybill and Wang(1980)에 의해 제안된 수정 대표본 방법에 의거한 신뢰구간 추정법이며 현재까지 다양한 실험계획 방법 하에서 분산 성분들의 여러 가지 형태의 함수들에 대하여 확장과 개량이 이루어져 왔다. 본 연구에서는 분산 성분 모형의 균형 실험 가정 하에서 분산 성분들의 선형 결합이 관심있는 모수일 때 분산 분석에 의해 얻어진 수정 대표본 신뢰구간의 실제 포함확률을 툴스트랩 보정을 이용하여 개선하는 방법에 대하여 논의한다. 붓스트랩 보정을 이용함으로서 신뢰구간의 포함 확률의 정도는 점근적 이차 차수까지 개선되며 특히 선형 결합의 계수들이 모두 양수이고 결합의 수가 증가할 경우 수정 대표본 신뢰구간의 포함확률이 주어진 신뢰계수보다 항상 커지게 되는 단점을 개선할 수 있음을 보인다. 제안된 붓스트랩 보정 신뢰구간의 효율을 소표본의 경우에 모의실험을 통하여 평가한다.

• 응용통계연구
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• 제6권2호
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• pp.227-235
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• 1993

순서쌍으로 주어진 자료 $(x_i, y_i), i=1,2,\cdots,n$ 들에 대한 독립변수와 관련된 추정은 회귀분석과는 달리 교정(calibration)이라고 불리워진다. 본 논문에서는 정규상 등과 같은 가정을 하지않고 비모수적인 커널방법을 이용하여 교정함수를 추정하고 추정된 교정함수의 붓스트랩 신뢰대를 이용한 독립변수의 구간추정을 제안하고자 한다. 교정과 커널방법에 대해 설명하였으며 독립변수의 추정에 대한 문헌적 고찰과 함께 붓스트랩 신뢰대에 대하여 첨언하였고 실제 자료를 통하여 다른방법과 비교, 분석하였다.

• Smart Structures and Systems
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• 제4권6호
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• pp.711-726
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• 2008

A number of efforts had been sought to instrument bridges for the purpose of structural monitoring and assessment. The outcome of these efforts, as gauged by advances in the understanding of the definition of structural damage and their role in sensor selection as well as in the design of cost and data-effective monitoring systems, has itself been difficult to assess. The authors' experience with the design, calibration, and operation of a monitoring system for the Kishwaukee Bridge in Illinois has provided several lessons that bear upon these concerns. The systems have performed well in providing a continuous, low-cost monitoring platform for bridge engineers with immediate relevant information.

• Journal of Gastric Cancer
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• 제15권4호
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• pp.262-269
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• 2015

Purpose: Intraabdominal abscess is one of the most common reasons for re-hospitalization after gastrectomy. This study aimed to develop a model for estimating the probability of intraabdominal abscesses that can be used during the postoperative period. Materials and Methods: We retrospectively reviewed the clinicopathological data of 1,564 patients who underwent gastrectomy for gastric cancer between 2010 and 2012. Twenty-six related markers were analyzed, and multivariate logistic regression analysis was used to develop the probability estimation model for intraabdominal abscess. Internal validation using a bootstrap approach was employed to correct for bias, and the model was then validated using an independent dataset comprising of patients who underwent gastrectomy between January 2008 and March 2010. Discrimination and calibration abilities were checked in both datasets. Results: The incidence of intraabdominal abscess in the development set was 7.80% (122/1,564). The surgical approach, operating time, pathologic N classification, body temperature, white blood cell count, C-reactive protein level, glucose level, and change in the hemoglobin level were significant predictors of intraabdominal abscess in the multivariate analysis. The probability estimation model that was developed on the basis of these results showed good discrimination and calibration abilities (concordance index=0.828, Hosmer-Lemeshow chi-statistic P=0.274). Finally, we combined both datasets to produce a nomogram that estimates the probability of intraabdominal abscess. Conclusions: This nomogram can be useful for identifying patients at a high risk of intraabdominal abscess. Patients at a high risk may benefit from further evaluation or treatment before discharge.

• Asian Pacific Journal of Cancer Prevention
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• 제15권16호
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• pp.6811-6817
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• 2014

Background: Breast cancer risk prediction models are widely used in clinical practice. They should be useful in identifying high risk women for screening in limited-resource countries. However, previous models showed poor performance in derived and validated settings. Therefore, we aimed to develop and validate a breast cancer risk prediction model for Thai women. Materials and Methods: This cross-sectional study consisted of derived and validation phases. Data collected at Ramathibodi and other two hospitals were used for deriving and externally validating models, respectively. Multiple logistic regression was applied to construct the model. Calibration and discrimination performances were assessed using the observed/expected ratio and concordance statistic (C-statistic), respectively. A bootstrap with 200 repetitions was applied for internal validation. Results: Age, menopausal status, body mass index, and use of oral contraceptives were significantly associated with breast cancer and were included in the model. Observed/expected ratio and C-statistic were 1.00 (95% CI: 0.82, 1.21) and 0.651 (95% CI: 0.595, 0.707), respectively. Internal validation showed good performance with a bias of 0.010 (95% CI: 0.002, 0.018) and C-statistic of 0.646(95% CI: 0.642, 0.650). The observed/expected ratio and C-statistic from external validation were 0.97 (95% CI: 0.68, 1.35) and 0.609 (95% CI: 0.511, 0.706), respectively. Risk scores were created and was stratified as low (0-0.86), low-intermediate (0.87-1.14), intermediate-high (1.15-1.52), and high-risk (1.53-3.40) groups. Conclusions: A Thai breast cancer risk prediction model was created with good calibration and fair discrimination performance. Risk stratification should aid to prioritize high risk women to receive an organized breast cancer screening program in Thailand and other limited-resource countries.