• Journal of the Korean School Mathematics Society
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• v.19 no.2
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• pp.123-151
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• 2016

The purpose of this study is to analyze the existing studies about the effect on private tutoring and EBS broadcasting which is considered as the alternative which was presented by education authorities. And this study attempts to measure the degree of the effects of private tutoring and EBS engagement on mathematics achievement using various quantitative methodologies. T-test and OLS multiple regression indicates some selection-bias which has positive direction compared to the PSM method closed to experimental design. So, it will be required to consider the methodology which measures the exact effect of institution or participation when we conduct the observational studies.

• Journal of Labour Economics
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• v.32 no.3
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• pp.91-121
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• 2009

Utilizing the fact that student allocation to private or public high schools in Korea is done randomly within a given school district, this study conducted a natural experiment, free from selection bias, to analyze whether private schools are more effective than public schools in terms of enhancing students' academic performance. After analyzing a model that controls the fixed effects of school districts, it was found that private schools do not have a statistically significant impact compared to public schools with respect to improving academic records. Nevertheless, the private school effect has shown a positive value equivalent to 0.13 standard deviation for female students at the highest academic levels.

• Survey Research
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• v.1 no.1
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• pp.73-108
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• 2000

This study investigates methodological implications of cyberspace and information technology for online survey research Online survey method provides useful methodological tools for collecting empirical data for the study of cyberspace, In terms of sampling frame , selection method, and questionnaire from four major types of the online survey research can be found: member survey visitor survey e-mail survey and the electronic survey. Online survey research with sample design(population specification error. sampling frame error, selection error) measurement (measurement instrument bias system-related processing error, nonrespone, and response bias) and research ethics (privacy and netiquette) pose important methodological issues for the survey. The realization of the technological possibilities of online survey will be possible only through a right consideration of these issues.

• Korea Journal of Hospital Management
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• v.21 no.4
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• pp.45-54
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• 2016

The purpose of this study is to identify patient and hospital characteristics with pulmonary tuberculosis and to analyze factors which were influencing length of stay and treatment. The Korean National Hospital Discharge In-depth Injury Survey database from 2006 to 2012 was used for analysis. Study subjects were 4,704 patients and analyzed by using frequency, chi-square and logistic regression through using STATA 12.0. To avoid selection bias, we used propensity score matching. Analysis results show that the length of stay and treatment of pulmonary tuberculosis was different between insurance types. Patients characteristic(female, comorbidity, admission by outpatient department, medical insurance type) and hospital characteristic(500-999 beds, over 1000 beds) significantly influence length of stay. Admission by outpatient department and over 1000 beds are significantly influence treatment. Based on these findings, it is necessary to clarify between length of stay and treatment outcome by medical aids beneficiaries and audit hospitals follow discharge guidelines in pulmonary tuberculosis patients.

• Journal of the Korean School Mathematics Society
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• v.18 no.1
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• pp.149-167
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• 2015

In this study, we estimate the effect of ability grouping on mathematics achievement empirically. We use propensity score matching(PSM) method to minimize selection bias and estimate the effect of ability grouping on the mathematics standard score of Scholastic Ability Test with the KELS(Korea Education Longitudinal Study) 6th stage data. The result indicated that relationship between ability grouping and mathematics achievement is positive and Policy efforts is needed to operate ability grouping effectively.

• The Journal of the Korea institute of electronic communication sciences
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• v.8 no.10
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• pp.1477-1483
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• 2013

This paper proposes a low-voltage current-mode integrator for a continuous-time current-mode baseband channel selection filter. The low-voltage current-mode linear cascode integrator is introduced to offer advantages of high current gain and improved unity-gain frequency. The proposed current-mode integrator has fully differential input and output structure consisting of CMOS complementary circuit. Additional cascode transistors which are operated in linear region are inserted for bias to achieve the low-voltage feature. Frequency range is also controllable by selecting proper bias voltage. From simulation results, it can be noticed that the implemented integrator achieves design specification such as low-voltage operation, current gain, and unity gain frequency.

• Journal of Korean Society of Rural Planning
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• v.30 no.1
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• pp.81-97
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• 2024

This study examines the effects of adopting Information and Communication Technology (ICT) in livestock farm management on farm sales revenue. Using the 2020 Census of Agriculture, Forestry, and Fisheries, a nationally representative data set constructed by Statistics Korea, this study focuses on a sample of 9,020 livestock farms in South Korea. We employ Propensity Score Matching (PSM) methods to address the potential selection bias between 2,076 farms that used ICT for livestock farm management and 6,944 farms that did not. The findings consistently show that the use of ICT significantly increases farm revenue, taking into account the selection bias. The utilization of ICT in livestock farms leads to a higher increase in sales revenue, particularly for farms with greater sales.

• The Journal of Korean Medicine Ophthalmology and Otolaryngology and Dermatology
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• v.30 no.3
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• pp.1-19
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• 2017

Objectives : This study aimed to validate the effect of herbal medicine intervention to relieve the symptoms of psoriasis using systematic review and meta-analysis and provide the newest reason of effectiveness of Korean medicine to psoriasis. Methods : Data were collected through electronic database including Pubmed, Cochrane CENTRAL, NDSL OASIS, Koreantk. Two experts assessed risk of bias of randomized controlled trials by Cochrane group's Risk of Bias tool after searching, reviewing and selecting papers. Data were analyzed using Review Manager(RevMan) 5.3 and Comprehensive Meta Analysis 2.0. Results : Total number of selected trials was 16 randomized controlled trials. This study evaluated the risk of bias and effectiveness of herbal medicine to psoriasis. There were high frequency uncertain in selection bias, performance bias and detection bias. In this meta-analysis, Korean medicine treatment was more effective than western medicine (ES:0.507, 95%CI:0.147-0.867) and placebo (ES:0.955, 95%CI:0.598-1.312). Conclusions : Herbal medicine intervention can be an effective for treatment in psoriasis. But enhancing levels of evidence, we must try to accumulate clinical researches of herbal medicine to psoriasis in Korea.

• Smart Media Journal
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• v.13 no.2
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• pp.44-51
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• 2024

The construction of a stress measurement detaset plays a curcial role in various modern applications. In particular, for the efficient training of artificial intelligence models for stress measurement, it is essential to compare various biases and construct a quality-controlled dataset. In this paper, we propose the construction of a stress measurement dataset with quality management through the comparison of various biases. To achieve this, we introduce strss definitions and measurement tools, the process of building an artificial intelligence stress dataset, strategies to overcome biases for quality improvement, and considerations for stress data collection. Specifically, to manage dataset quality, we discuss various biases such as selection bias, measurement bias, causal bias, confirmation bias, and artificial intelligence bias that may arise during stress data collection. Through this paper, we aim to systematically understand considerations for stress data collection and various biases that may occur during the construction of a stress dataset, contributing to the construction of a dataset with guaranteed quality by overcoming these biases.

• Restorative Dentistry and Endodontics
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• v.45 no.3
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• pp.28.1-28.13
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• 2020

Objectives: To evaluate the outcome of in vitro studies comparing the effectiveness of QMix irrigant in removing the smear layer in the root canal system compared with other irrigants. Materials and Methods: The research question was developed by using Population, Intervention, Comparison, Outcome and Study design framework. Literature search was performed using 3 electronic databases PubMed, Scopus, and EBSCOhost until October 2019. Two reviewers were independently involved in the selection of the articles and data extraction process. Risk of bias of the studies was independently appraised using revised Cochrane Risk of Bias tool (RoB 2.0) based on 5 domains. Results: Thirteen studies fulfilled the selection criteria. The overall risk of bias was moderate. QMix was found to have better smear layer removal ability than mixture of tetracycline isonomer, an acid and a detergent (MTAD), sodium hypochlorite (NaOCl), and phytic acid. The efficacy was less effective than 7% maleic acid and 10% citric acid. No conclusive results could be drawn between QMix and 17% ethylenediaminetetraacetic acid due to conflicting results. QMix was more effective when used for 3 minutes than 1 minute. Conclusions: QMix has better smear layer removal ability compared to MTAD, NaOCl, Tubulicid Plus, and Phytic acid. In order to remove the smear layer more effectively with QMix, it is recommended to use it for a longer duration.