• Journal of the Korean Geotechnical Society
• /
• v.30 no.8
• /
• pp.25-37
• /
• 2014

In load and resistance factor design (LRFD) method, resistance factors are typically calibrated using resistance bias factors obtained from either only the data within ${\pm}2{\sigma}$ or the data except the tail values of an assumed probability distribution to increase the reliability of the database. However, the data selection approach has a shortcoming that any low-quality data inadvertently included in the database may not be removed. In this study, a data quality evaluation method, developed based on the quality of static load test results, the engineering characteristics of in-situ soil, and the dimension of aggregate piers, is proposed for use in constructing database. For the evaluation of the method, a total 65 static load test results collected from various literatures, including static load test reports, were analyzed. Depending on the quality of the database, the comparison between bias factors, coefficients of variation, and resistance factors showed that uncertainty in estimating bias factors can be reduced by using the proposed data quality evaluation method when constructing database.

• Journal of Korean Society of Transportation
• /
• v.18 no.6
• /
• pp.63-75
• /
• 2000

Stated Preference (SP) data has been regarded as more useful than Revealed Preference (RP) data, because researchers can investigate the respondents\` Preference and attitude for a traffic condition or a new traffic system by using the SP data. However, the SP data has two bias: the first one is the bias inherent in SP data and the latter one is the attrition bias in SP panel data. If the biases do not corrected, the choice model using SP data may predict a erroneous future demand. In this Paper, six route choice models are constructed to deal with the SP biases, and. these six models are classified into cross-sectional models (model I∼IH) and dynamic models (model IV∼VI) From the six models. some remarkable results are obtained. The cross-sectional model that incorporate RP choice results of responders with SP cross-sectional model can correct the biases inherent in SP data, and also the dynamic models can consider the temporal variations of the effectiveness of state dependence in SP responses by assuming a simple exponential function of the state dependence. WESML method that use the estimated attrition probability is also adopted to correct the attrition bias in SP Panel data. The results can be contributed to the dynamic modeling of SP Panel data and also useful to predict more exact demand.

• Journal of the Korean Data and Information Science Society
• /
• v.24 no.4
• /
• pp.815-824
• /
• 2013

Traditional Pearson chi-squared test is not appropriate for the data collected by the complex sample design. When one uses the traditional Pearson chi-squared test to the complex sample categorical data, it may give wrong test results, and the error may occur not only due to the biased variance estimators but also due to the biased point estimators of cell proportions. In this study, the design based consistent Wald test statistics was derived for k-population homogeneity test, and the traditional Pearson chi-squared test statistics was partitioned into three parts according to the causes of error; the error due to the bias of variance estimator, the error due to the bias of cell proportion estimator, and the unseparated error due to the both bias of variance estimator and bias of cell proportion estimator. An analysis was conducted for empirical results of the relative size of each error component to the Pearson chi-squared test statistics. The second year data from the fourth Korean national health and nutrition examination survey (KNHANES, IV-2) was used for the analysis. The empirical results show that the relative size of error from the bias of variance estimator was relatively larger than the size of error from the bias of cell proportion estimator, but its degrees were different variable by variable.

• Communications for Statistical Applications and Methods
• /
• v.17 no.4
• /
• pp.515-525
• /
• 2010

We investigated design-based properties of the ordinary least square estimator(OLSE) and the weighted least square estimator(WLSE) in a panel regression model. Given a complex data we derive the magnitude of the design-based bias of two estimators and show that the bias of WLSE is smaller than that of OLSE. We also conducted a simulation study using Korean welfare panel data in order to compare design-based properties of two estimators numerically. In the study we found the followings. First, the relative bias of OLSE is nearly two times larger than that of WLSE and the bias ratio of OLSE is greater than that of WLSE. Also the relative bias of OLSE remains steady but that of WLSE becomes smaller as the sample size increases. Next, both the variance and mean square error(MSE) of two estimators decrease when the sample size increases. Also there is a tendency that the proportion of squared bias in MSE of OLSE increases as the sample size increase, but that of WLSE decreases. Finally, the variance of OLSE is smaller than that of WLSE in almost all cases and the MSE of OLSE is smaller in many cases. However, the number of cases of larger MSE of OLSE increases when the sample size increases.

• Korean Journal of Occupational Health Nursing
• /
• v.25 no.3
• /
• pp.199-207
• /
• 2016

Purpose: The purpose of this study was to identify the obesity stress, weight bias and health care on Body Mass Index (BMI) in soldiers of non-combat area and to provide data for improving the quality of their life. Methods: This research involved 165 soldiers working in non-combat area. Data collection was conducted from November 1 to 20, 2015. Statistical analysis of the collected data were t-test and ANOVA, $Scheff{\acute{e}}$ method post hoc analysis, Pearson's correlation coefficients, and multiple liner regression using IBM SPSS 22.0. Results: The mean score of obesity stress was moderate ($19.05{\pm}5.28$). The mean score of weight bias was 69.03 and health care was 2.41 points. There are a positive correlation between obesity stress and BMI (r=.19, p<.05). Weight bias (r=-.19, p<.01) and health care (r=-.26, p<.01) among the subjects had negative correlations with BMI. In a multiple liner regression, obesity stress (${\beta}=.18$, p<.05), health care (${\beta}=-.18$, p<.05) were associated with BMI. Conclusion: Based on the findings that obesity stress and health care influence BMI, there is a need to control stress and to properly set proper guidelines on health care for soldiers.

• Journal of the Korean Data and Information Science Society
• /
• v.27 no.5
• /
• pp.1317-1325
• /
• 2016

The purpose of this paper is to explain the factors affecting the wage of the vocational high school graduates. We particularly examine the effectiveness of controlling sample selection bias by employing the Tobit model and Heckman sample selection model. The major results are as follows. First it is shown that the Tobit model and Heckman sample selection model controlling sample selection bias is statistically significant. Hence all the independent variables seem to be statistically consistent with the theoretical model. Second, gender was statistically significant, both in the probability of employment and the wage. Third, the employment probability and wage of Maester high school graduates were shown to be high compared to all other graduates. Fourth, the higher parent's income, the higher are both the employment probability and the wage. Finally, parents education level, high school grade, satisfaction, and a number of licenses were found to be statistically significant, both in the probability of employment and wages.

• Korean Parent-Child Health Journal
• /
• v.22 no.1
• /
• pp.22-29
• /
• 2019

Purpose: This study was conducted to identify the intention of visiting obstetrics and gynecology of female college students by considering their perception and optimistic bias. Methods: The study included a total of 135 female college students under the age of 25. The data collection period is a descriptive research study conducted online from April 8, 2019 to April 16, 2019. The collected data were analyzed using the correlation of t-test, ANOVA, Pearson's correlation and multiple regression using SPSS 20.0. Results: The degree of intention of behavior for visits to obstetrics and gynecology was $3.10{\pm}1.06points$ on average. Intention of behavior for visits to obstetrics and gynecology had significant variance depending on sexual experience (t=3.09, p<.001). The intention of behavior for visits to obstetrics and gynecology had positive correlations with the cognition of visits to obstetrics and gynecology (r=.422, p<.001), the optimism bias (r=.419, p<.001). Influence factors emerged the optimism bias, cognition and sexual experience with explanatory power of 30.4%. Conclusion: The results of this paper can be used to prepare the basic data for the development of educational programs to promote preventive gynecological visits of female college students. Through this, the preventive screening rate, the quality of reproductive health in women's lives.

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

• Journal of The Korean Society of Integrative Medicine
• /
• v.10 no.4
• /
• pp.71-81
• /
• 2022

Purpose : This study aimed to present evidence by analyzing the characteristics and effectiveness of group art therapy interventions through an examination of domestic studies on group art therapy for older people with dementia. Methods : The database used DBpia, Riss, and Google Scholar, and the research period was from 2016 to November 2021. For the selected studies, the level of evidence was analyzed, bias evaluation was performed, and patient, intervention, comparison, and outcome were analyzed. For the evaluation of bias, the risk of bias assessment tool for non-randomized study (RoBANS) and Cochrane's risk of bias (RoB) were used. Results : As for the level of evidence of the included studies, level I consisted of five studies, and levels II and III each had one article. As a result of the bias evaluation of five studies through RoB, a "low risk of bias" was found for incomplete result data, selective result reporting, and others, except for four unclear evaluation areas. The "low risk of bias" ratio was 0~25 % in the evaluation of bias in two studies through RoBANS. For the evaluation tool, cognitive evaluation tool was used the most while mini-mental state examination-Korea was used the most frequently. For the intervention method, the most frequently used was group art therapy that employed recall in three studies, while collage, Korean painting, use of paper media, and procedural memory were used in each of the other studies. Each intervention was found to be significantly effective overall. Conclusion : This study provided clinical evidence by systematically reporting research on group art therapy for older people with dementia. In the future, it is necessary to check the effect of group art therapy on various areas other than cognition for older people with dementia. Moreover, the study should be conducted with the risk of bias sufficiently taken into consideration.

• Journal of Distribution Science
• /
• v.18 no.4
• /
• pp.79-85
• /
• 2020

Purpose: This study explores how cognitive impairment caused by social exclusion experience can be explained through cognitive narrowing and how it influences consumer's judgment and reasoning and results pseudodiagnosticity bias towards distribution brands. This study examines the characteristics of cognitive narrowing, which is one of the strategies for overcoming the negative emotions resulting from social exclusion, and how cognitive errors called pseudodiagnosticity bias occur due to cognitive narrowing in the evaluation of distribution brands. Research design, data and methodology: Present study was performed with 77 college students in Seoul. Participants were randomly assigned to the group who experienced social exclusion and the group who did not experience social exclusion. The analysis has been made of how the degree of bias of pseudodiagnosticity differs according to the experience of social exclusion by t-test. Results: The group who experienced social exclusion had a higher level of pseudodiagnosticity bias towards distribution brands than the group who did not experience social exclusion. Conclusions: This study confirmed what characteristics of cognitive narrowing, which is one of the strategies for overcoming the negative emotions resulting from social exclusion, and how cognitive errors called pseudodiagnosticity bias occur due to cognitive narrowing. Implications and future research directions were discussed and suggested.