• Korean Journal of Acupuncture
• /
• 제35권2호
• /
• pp.70-81
• /
• 2018

Objectives : To investigate the association of trial registration status with presence of reporting bias including publication bias and outcome reporting bias in recently published randomized controlled trials (RCTs) of acupuncture. Methods : A PubMed search for RCTs of acupuncture published from March 2016 to February 2017 was conducted. Primary outcomes were identified and the direction of the results was judged as positive (i.e., statistically significant) or negative. The trial registration was identified by manually screening the trial registration number in the main text of the published article and classified into 1) prospective registration; 2) retrospective registration based on the registration date or; 3) no registration. Results : Of the 125 included RCTs, only 40 studies (32.0%) prospectively registered the study protocols. Among 65 RCTs that adequately reported the primary outcome, unregistered trials were more likely to report positive results than the registered ones (p=0.013). Of the 40 prospectively registered studies, 19 trials (47.5%) had the discrepancies between the registered and published primary outcomes and furthermore, 40% of them reported the positive findings. Conclusions : Unregistered trials were more likely to report positive results and the discrepancies between the registered and published primary outcomes were detected in about a half of the prospectively registered studies, 42.1% of which tended to report positive findings. Journal editors and researchers in this field should be alerted to various reporting biases.

• Investigative Magnetic Resonance Imaging
• /
• 제23권2호
• /
• pp.114-124
• /
• 2019

Purpose: We investigate biases in the assessments of left ventricular function (LVF), by compressed sensing (CS)-cine magnetic resonance imaging (MRI). Materials and Methods: Cardiovascular cine images with short axis view, were obtained for 8 volunteers without CS. LVFs were assessed with subsampled data, with compression factors (CF) of 2, 3, 4, and 8. A semi-automatic segmentation program was used, for the assessment. The assessments by 3 CS methods (ITSC, FOCUSS, and view sharing (VS)), were compared to those without CS. Bland-Altman analysis and paired t-test were used, for comparison. In addition, real-time CS-cine imaging was also performed, with CF of 2, 3, 4, and 8 for the same volunteers. Assessments of LVF were similarly made, for CS data. A fixed compensation technique is suggested, to reduce the bias. Results: The assessment of LVF by CS-cine, includes bias and random noise. Bias appeared much larger than random noise. Median of end-diastolic volume (EDV) with CS-cine (ITSC or FOCUSS) appeared -1.4% to -7.1% smaller, compared to that of standard cine, depending on CF from (2 to 8). End-systolic volume (ESV) appeared +1.6% to +14.3% larger, stroke volume (SV), -2.4% to -16.4% smaller, and ejection fraction (EF), -1.1% to -9.2% smaller, with P < 0.05. Bias was reduced from -5.6% to -1.8% for EF, by compensation applied to real-time CS-cine (CF = 8). Conclusion: Loss of temporal resolution by adopting missing data from nearby cardiac frames, causes an underestimation for EDV, and an overestimation for ESV, resulting in underestimations for SV and EF. The bias is not random. Thus it should be removed or reduced for better diagnosis. A fixed compensation is suggested, to reduce bias in the assessment of LVF.

• 대기
• /
• 제31권2호
• /
• pp.215-227
• /
• 2021

The necessity of the prediction on the Seasonal-to-Subseasonal (S2S) timescale continues to rise. It led a series of studies on the S2S prediction models, including the Global Seasonal Forecasting System Version 5 (GloSea5) of the Korea Meteorological Administration. By extending previous studies, the present study documents sea surface temperature (SST) prediction skill around the Korean peninsula in the GloSea5 hindcast over the period of 1991~2010. The overall SST prediction skill is about a week except for the regions where SST is not well captured at the initialized date. This limited prediction skill is partly due to the model mean biases which vary substantially from season to season. When such biases are systematically removed on daily and seasonal time scales the SST prediction skill is improved to 15 days. This improvement is mostly due to the reduced error associated with internal SST variability during model integrations. This result suggests that SST around the Korean peninsula can be reliably predicted with appropriate post-processing.

• 한국인터넷방송통신학회논문지
• /
• 제22권1호
• /
• pp.163-170
• /
• 2022

본 논문은 실생활 속 정제되지 않은 입력으로 인해 안면의 특징점을 추출하여 객체 인식 모델의 이상적인 성능과 속도를 보증해주지 못하는 문제점을 가중치 합산을 통한 저장 알고리즘을 통해 개선하는 방법을 소개한다. 많은 안면인식 프로세스들은 이상적인 상황에서의 정확도를 보장해주지만, 실생활에서 발생할 수 있는 수많은 방해요인에 대해서는 대처하지 못한다는 문제점이 주목받고 있으며 이는 곧 보안과 밀접하게 관련된 안면인식 프로세스에서 심각한 문제를 발생할 수도 있다. 본 논문에서는 사람의 고유한 특징점은 사진의 구도 등의 여러 변수가 있어도 결국 평균적인 하나의 형태를 띤다는 점을 이용하여 입력으로 추출된 특징점을 여러 방해 요인에 과적합 되어있지 않은 소수의 특징점과 비교를 통해 실시간으로 빠르게, 그리고 정확하게 안면인식을 할수 있는 방법을 가중치 합산방식을 통하여 제시한다.

• 천문학회보
• /
• 제46권2호
• /
• pp.40.3-41
• /
• 2021

Minor mergers leave behind long lived, but extremely faint and extended tidal features including tails, streams, loops and plumes. These act as a fossil record for the host galaxy's past interactions, allowing us to infer recent accretion histories and place constraints on the properties and nature of a galaxy's dark matter halo. However, shallow imaging or small homogeneous samples of past surveys have resulted in weak observational constraints on the role of galaxy mergers and interactions in galaxy assembly. The Rubin Observatory, which is optimised to deliver fast, wide field-of-view imaging, will enable deep and unbiased observations over the 18,000 square degrees of the Legacy Survey of Space and Time (LSST), resulting in samples of potentially of millions of objects undergoing tidal interactions. Using realistic mock images produced with state-of-the-art cosmological simulations we perform a comprehensive theoretical investigation of the extended diffuse light around galaxies and galaxy groups down to low stellar mass densities. We consider the nature, frequency and visibility of tidal features and debris across a range of environments and stellar masses as well as their reliability as an indicator of galaxy accretion histories. We consider how observational biases such as projection effects, the point-spread-function and survey depth may effect the proper characterisation and measurement of tidal features, finding that LSST will be capable of recovering much of the flux found in the outskirts of L* galaxies at redshifts beyond local volume. In our simulated sample, tidal features are ubiquitous In L* galaxies and remain common even at significantly lower masses (M*>10^10 Msun). The fraction of stellar mass found in tidal features increases towards higher masses, rising to 5-10% for the most massive objects in our sample (M*~10^11.5 Msun). Such objects frequently exhibit many distinct tidal features often with complex morphologies, becoming increasingly numerous with increased depth. The interpretation and characterisation of such features can vary significantly with orientation and imaging depth. Our findings demonstrate the importance of accounting for the biases that arise from projection effects and surface-brightness limits and suggest that, even after the LSST is complete, much of the discovery space in low surface-brightness Universe will remain to be explored.

• 대한토목학회논문집
• /
• 제28권3D호
• /
• pp.437-444
• /
• 2008

본 연구는 IKONOS-2 위성영상의 센서모델인 RPC 모델에 존재하는 편의들을 항공레이저측량 자료를 활용하여 보정하고 이를 통해 IKONOS-2 위성영상과 항공레이저측량 자료를 정합하기 위해 다양한 조정방정식을 적용하고 이를 검증하는 것을 목적으로 한다. 이를 위해 거리자료인 항공레이저측량 자료와 영상자료인 IKONOS-2 위성영상의 특성을 고려하여, 선형객체를 편의 수정을 위한 기하보정의 기본요소로 활용하였다. 이 때, IKONOS-2 위성영상의 RPC 모델에 존재하는 편의들은 항공레이저측량 자료로부터 추출된 선형객체들을 이용하여 영상좌표계 상에서 조정되게 된다. 특히, 본 연구에서는 IKONOS-2 위성영상의 RPC 모델의 편의보정을 위해 선행연구들에서 제시된 다양한 형태의 변환함수들에 대해 기하보정 방법론을 적용하고, 사용되는 변환함수에 따른 기하보정의 정확도 평가를 수행하였다. 또한, 기하보정에 사용되는 선형객체의 개수가 결과에 미치는 영향에 대한 평가도 동시에 수행하였다. 마지막으로 DGPS 측량을 통하여 획득된 검사점들을 활용하여 정확도 평가를 수행하고 연구결과의 효용성을 검증하였다.

• 산업경영시스템학회지
• /
• 제46권3호
• /
• pp.109-122
• /
• 2023

As platforms become primary decision making tools, platforms for decision have been introduced to improve quality of decision results. Because, decision platforms applied augmented decision-making process which uses experiences and feedback of users. This process creates a variety of alternatives tailored for users' abilities and characteristics. However, platform users choose alternatives before considering significant quality factors based on securing decision quality. In real world, platform managers use an algorithm that distorts appropriate alternatives for their commercial benefits. For improving quality of decision-making, preceding researches approach trying to increase rational decision -making ability based on experiences and feedback. In order to overcome bounded rationality, users interact with the machine to approach the optional situation. Differentiated from previous studies, our study focused more on characteristics of users while they use decision platforms. This study investigated the impact of quality factors on decision-making using platforms, the dimensions of systematic factors and user characteristics. Systematic factors such as platform reliability, data quality, and user characteristics such as user abilities and biases were selected, and measuring variables which trust, satisfaction, and loyalty of decision platforms were selected. Based on these quality factors, a structural equation research model was created. A survey was conducted with 391 participants using a 7-point Likert scale. The hypothesis that quality factors affect trust was proved to be valid through path analysis of the structural equation model. The key findings indicate that platform reliability, data quality, user abilities, and biases affect the trust, satisfaction and loyalty. Among the quality factors, group bias of users affects significantly trust of decision platforms. We suggest that quality factors of decision platform consist of experience-based and feedback-based decision-making with the platform's network effect. Through this study, the theories of decision-making are empirically tested and the academic scope of platform-based decision-making has been further developed.

• 한국통계학회:학술대회논문집
• /
• 한국통계학회 2002년도 춘계 학술발표회 논문집
• /
• pp.19-24
• /
• 2002

The two-way balanced one-level rotation design has been discussed (Park, Kim and Choi, 2001), where the two-way balancing is done on interview time in monthly sample and rotation group. We extend it to three-way balanced multi-level design under the most general rotation system. The three-way balancing is accomplished on interview time not only in monthly sample and rotation group but also in recall time. We present the necessary condition and rotation algorithm which guarantee the three-way balancing. We propose multi-level composite estimators (MCE) from this design and derive their variances and mean squared errors (MSE), assuming the correlation from the measurements of the same sample unit and three types of biases in monthly sample.

• 한국경영과학회지
• /
• 제34권2호
• /
• pp.91-100
• /
• 2009

"How does advertising affect sales?" is the fundamental issue of modern advertising research. There is an interesting issue for estimating carryover effects of advertising on sales, and the aggregated data biases exist in the duration of advertising effect. This research suggests an extended model of Koyck Model which is employed for micro-data (Koyck 1954) to estimate aggregated advertising data, and empirically shows the aggregated data bias. Our developed model with the aggregated level of actual advertising data is more appropriate than the basic Koyck model for micro-data. The result figures out that it is important to consider the disaggregated data level in the analysis of dynamic effects of adverting such as carryover effects.

• Communications for Statistical Applications and Methods
• /
• 제21권1호
• /
• pp.1-9
• /
• 2014

This paper discusses the problem of estimation of finite population mean in double sampling for stratification. In fact, ratio and product type exponential estimators of population mean are proposed in double sampling for stratification. The biases and mean squared errors of proposed estimators are obtained upto the first degree of approximation. The proposed estimators have been compared with usual unbiased estimator, ratio and product estimators in double sampling for stratification. To judge the performance of the proposed estimators an empirical study has been carried out.