• Journal of the Korea Convergence Society
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• v.12 no.4
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• pp.267-274
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• 2021

This study used data from the 6rd and 12th year of the Korean Welfare Panel to evaluate the effects of the Personal Assistance Service(PAS) system on the labor market of PAS users' participation. For the purpose of this study, 64 program groups using the Korean PAS and 344 control groups not using the Korean PAS were selected using Caliper matching among the propensity score matching. A chi-square test was used for the difference in characteristics between groups, and a simple difference-in-differences (DID) model and a double-difference multiple regression analysis of DID were performed to estimate the effect of thepolicy before and after the Korean PAS. As a result of the study, it was found that statistically, PAS had no significant effect on the labor market. This is due to the low number of system users, resulting in low post-hoc power, incomplete matching and limited availability of PAS Assistants for Disabled People. Therefore, In order to demonstrate the effectiveness of the Personal Assistance Service(PAS) system, specialized services and systems that meet the needs of the disabled and household members should be implemented.

• The Korean Journal of Applied Statistics
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• v.34 no.3
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• pp.309-327
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• 2021

Dynamic treatment regimes (DTRs) are decision-making rules designed to provide personalized treatment to individuals in multi-stage randomized trials. Unlike classical methods, in which all individuals are prescribed the same type of treatment, DTRs prescribe patient-tailored treatments which take into account individual characteristics that may change over time. The Q-learning method, one of regression-based algorithms to figure out optimal treatment rules, becomes more popular as it can be easily implemented. However, the performance of the Q-learning algorithm heavily relies on the correct specification of the Q-function for response, especially in observational studies. In this article, we examine a number of double-robust weighted least-squares estimating methods for Q-learning in high-dimensional settings, where treatment models for propensity score and penalization for sparse estimation are also investigated. We further consider flexible ensemble machine learning methods for the treatment model to achieve double-robustness, so that optimal decision rule can be correctly estimated as long as at least one of the outcome model or treatment model is correct. Extensive simulation studies show that the proposed methods work well with practical sample sizes. The practical utility of the proposed methods is proven with real data example.

• Korean Journal of Cognitive Science
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• v.28 no.1
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• pp.1-26
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• 2017

This study investigated the cortical generators of P300 in college students with schizotypal traits by using an auditory oddball paradigm, event-related potentials (ERPs) and standardized low resolution brain electromagnetic tomography (sLORETA) model. We also investigated the relationship between the current density of P300 and the clinical symptoms of schizophrenia. Based on the scores of Schizotypal Personality Questionnaire(SPQ), schizotypal trait (n=37) and control (n=42) groups were selected. For the measurement of P300, an auditory oddball paradigm, in which frequent standard tones (1000Hz) and rare target tones (1500Hz) were presented randomly, was used. Participants were required to count the number of the target tones during the task and report this at the end of the experiment. The two groups did not differ significantly in the accuracy of the oddball task. The schizotypal trait group showed significantly smaller P300 amplitudes than control group. In terms of source localization, both groups showed the P300 current density over bilateral frontal, parietal, temporal and occipital lobes. However, the schizotypal trait group showed significantly reduced activations in the left superior temporal gyrus and the right middle temporal gyrus, but increased activations in both left inferior frontal gyrus and right superior frontal gyrus compared to the control group. Furthermore, a negative correlation between the current density of the right superior frontal gyrus and SPQ disorganization score was found in the schizotypal trait group. These findings indicate that the individuals with schizotypal traits have dysfunctions of frontal and temporal areas, which are known to be the source of P300, as observed in patients with schizophrenia. In addition, the present results indicate that the disorganization score, rather than total score, of the SPQ is useful in predicting the risk of future schizophrenia.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.11 no.9
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• pp.3223-3231
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• 2010

For a long time, most of advanced countries have supported the innovative firms with various support methods such as tax credit, subsidy, human resource education, and so on. Tax credit for innovation is the most popular industrial policy in these countries including Korea. However, in Korea, the effect of tax credit policy has been rarely analyzed. On the other hand, a considerable number of studies discover that tax credit policy in other countries influences positively on invest of R&D expenditure. This paper shows that tax credit policy positively influences on firm's innovation performances in Korea. The evaluated innovative effect of tax credit policy in this paper is more persuasive because it introduces various innovation performance variables including patent application with Propensity score matching method(PSM).

• Korean Journal of Social Welfare Studies
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• v.45 no.2
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• pp.5-30
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• 2014

This study sought to identify developmental trajectories of bullying victimization from late elementary school through early high school, and to examine internalizing and externalizing problem outcomes associated with the trajectory group membership. Data from Seoul Panel Study of Children were collected annually over a 7-year period from 5th grade of elementary school through 2nd grade of high school (2005~2011). Latent class growth analysis yield three trajectory classes corresponding to stable low (81.2%), stable high (3.5%), and declining bullying victimization (15.6%). Findings from analysis of covariance indicated that students in both stable high and declining trajectory groups reported significantly higher means in internalizing behavior (withdrawal, depression/anxiety, and suicide ideation), compared to those in the stable low group. For externalizing behavior such as aggression and juvenile status offense, students in the stable high group showed higher means, compared to those in the stable low and declining trajectory groups. Developmental pattern of bullying victimization over multiple development stages and associated internalizing and externalizing outcomes are discussed as are the implications for the bullying prevention.

• KDI Journal of Economic Policy
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• v.34 no.3
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• pp.133-186
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• 2012

This paper analyzes the effectiveness of social networks in finding jobs and estimates the value of job search network using the Korean Laber and Income Panel Study (KLIPS) dataset and utilizing the Difference-in-Difference Propensity Score Matching (PSM) methodology (Heckman et al., 1997). While the wide use of social networks in the Korean labor market is often perceived as 'nepotism,' this study confirms that social networks, by serving as an effective information transmitter between job search and recruitment, make a significant contribution to improving the adequacy of job matching in the domestic labor market. In order to verify the effectiveness of using social networks for getting jobs, this study looks into the cases of labor turnover using social networks and also not using it. In the aspect of individual satisfaction improvement relating to workplace and job duties, both cases of turnover turn out to experience an increased satisfaction by 2~3 points (on a 100-score scale). Meanwhile, as for the educational and technical adequacy improvement, no positive effects are found in the case of turnover without social networks, whereas the educational and technical adequacy improvement turns out to increase by 2.13 and 2.52 points, respectively, in the case of turnover using social networks. The effect of income increase through turnover using social networks registered 40,074 Korean won per month (as of 2010), which can be considered as the result from the improved educational and technical adequacy. Of all things being considered, the value of job search network per wage worker in the Korean society is estimated to be 18.72 million won in terms of life-cycle wage improvement, and 758.2 scores in terms of the improvement of working life satisfaction. Provided that the cash value of satisfaction score 1 is equivalent to 'n' times 10,000 won, the aggregate value of job search network is estimated to be 18.72+7.582n million won, which means the total amount of costs that a wage worker in the Korean society willingly pays to maintain and manage job networks for lifetime.