Private tutoring and its impact on students' academic achievement, formal schooling, and educational inequality in Korea

Over the last two decades, private tutoring has emerged as an important issue in education as its demand has been growing around the world. However, the evidence of the effectiveness of private tutoring is still mixed. Using the Korean Educational Longitudinal Survey, this dissertation explores the causal impact of private tutoring in Korea on three outcomes: students' academic achievement, the quality of the learning environment in formal schooling, and educational inequality. The first set of empirical analyses explores how private tutoring in secondary schools affects students' academic achievement in both short-term and long-term aspects using Ordinary Least Squares, Instrumental Variable, and Propensity Score Matching methods. The results suggest that private tutoring in middle school, on average, has positive short-term effects on students' academic achievement in middle school, but minimal long-term effects on the university entrance examination scores. By subject area, English and math tutoring are effective in improving academic achievement in middle school, whereas verbal tutoring is not. Moreover, private tutoring in grade 7 is most beneficial for students in middle school. In terms of private tutoring in high school, only math tutoring is beneficial for high school students in improving scores on the university entrance examination. The second set of the analyses employs Ordered Logit, Propensity Score Matching, and Difference-in-Differences methods to estimate the impact of private tutoring on the quality of formal schooling. The quality of the learning environment in formal schooling is measured by students' attention to lessons in class. On average, private tutoring shows a positive influence on students' attention to lessons in grade 8, but the magnitude of its influence is not substantial. However, when differentiating the results by ability group, positive effects are detected mostly in the low-ability group, which means that low achievers pay more attention to lessons in schools if they participate in private tutoring. These results imply that private tutoring improves the overall learning environment in formal schooling, which in turn increases the overall quality of schooling. The third set of the analyses uses Quantile Regression, Two-Stage Least Absolute Deviation estimator, and Propensity Score Subclassification to estimate the heterogeneous effects of private tutoring between ability groups, which provides implications on educational inequality based on academic achievement. The overall results suggest that private tutoring in middle school exacerbates educational inequality between high and low achievers, which implies a widening of the achievement gap. In addition, enrolling in tutoring at an earlier grade level results in greater heterogeneity between high and low achievers in academic performance than enrolling in tutoring during later grade levels. However, private tutoring in high school contributes to reducing the achievement gap; low achievers benefit more from private tutoring in high school compared to high achievers. Moreover, three years of cumulative math tutoring and receiving a single year of math tutoring in grade 12 contribute to narrowing the achievement gap between low and high achievers in the university entrance examination scores

A study on postpartum symptoms and their related factors in Korea

AbstractObjectiveThis study was aimed to identify the physical and mental state of women after delivery, to investigate the factors that influence those, and to examine the effects of postpartum care performance, which is traditionally believed to be appropriate care in Korea, on women's physical and mental status.Materials and MethodsA total of 148 women who visited our hospital for postpartum check-up on the 2nd week or 6th week after delivery were selected. We researched postpartum care methods using a questionnaire and had the women self-evaluate their postpartum symptoms. Depression was evaluated using the Beck Depression Inventory.ResultsThe average points of the 27 postpartum symptoms was 2.70 points (from 1 = very good to 5 = very bad). Seventy-two women had depression. Factors related to postpartum symptoms and depression were smoking before pregnancy, low marital satisfaction, bad mood during and after pregnancy, lack of support from husbands, and bad quality of sleep during puerperium. Treating the joints of hands carefully when milking breasts, and avoiding squatting down, demonstrated a negative correlation with the average points of postpartum symptoms. Multivariate linear regression analysis showed that mood during puerperium and Beck Depression Inventory points were significant factors related to the average points of postpartum symptoms and that the degree of support from husbands and mood during pregnancy were statistically related with depression.ConclusionMany women complained of postpartum discomfort. Although, while some postpartum care methods which are traditionally believed to be appropriate care in Korea can be helpful to women's recovery, most of them are not. We confirmed that physical symptoms and depression are closely related to each other

Merger relics of cluster galaxies

Context. Sheen and collaborators recently found that a surprisingly large portion (38%) of massive early-type galaxies in heavy clusters show strong merger-related disturbed features. This contradicts the general understanding that massive clusters are hostile environments for galaxy mergers. Considering the significance of mergers in galaxy evolution, it is important to understand this. Aims. We aim to present a theoretical foundation that explains galaxy mergers in massive clusters. Methods. We used the N-body simulation technique to perform a cosmological-volume simulation and derive dark-halo merger trees. Then, we used the semi-analytic modeling technique to populate each halo with galaxies. We ran hydrodynamic simulations of galaxy mergers to estimate the lifetime of merger features for the imaging condition used by Sheen and collaborators. We applied this merger feature lifetime to our semi-analytic models. Finally, we counted the massive early-type galaxies in heavy model clusters that would show strong merger features. Results. While there still are substantial uncertainties, our preliminary results are remarkably close to the observed fraction of galaxies with merger features. Key ingredients for the success are twofold: firstly, the subhalo motion in dark haloes has been accurately traced, and, second, the lifetime of merger features has been properly estimated. As a result, merger features are expected to last very long in cluster environments. Many massive early-type galaxies in heavy clusters therefore show merger features not because they experience mergers in the current clusters in situ, but because they still carry their merger features from their previous halo environments. Conclusions. Investigating the merger relics of cluster galaxies is potentially important, because it uniquely allows us to backtrack the halo merger history.Comment: 4 pages, 3 figures, accepted for publication in A&A Research Not

System reliability analysis of the scoliosis disorder.

BACKGROUND: Scoliosis is a spine abnormal deviation, which is an idiopathic disorder among children and adolescents. As a matter of the fact, distribution of loads on the patient\u27s spine and load-carrying capacity of the vertebral column are both random variables. Therefore, the probabilistic approach may consider as a sophisticated method to deal with this problem. METHOD: Reliability analysis is a probabilistic-based approach to consider the uncertainties of load and resistance of the vertebral column. The main contribution of this paper is to compare the reliability level of a normal and scoliosis spinal. To do so, the numerical analyses associated with the inherent random parameters of bones and applied load are performed. Then, the reliability indices for all vertebrae and discs are determined. Accordingly, as the main innovation of this paper, the system reliability indices of the spinal column for both normal and damaged backbone systems are represented. RESULTS: Based on the required reliability index for normal spinal curvature the target system reliability level for scoliosis disorder is proposed. CONCLUSION: Since the proposed target reliability index is based on the strength limit state of the vertebral column, it can be considered as a reliability level for any proposed treatment approaches