• Korean Journal of Social Welfare
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• v.30
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• pp.112-138
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• 1996

• Proceedings of the Botanical Society of Korea Conference
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• 1996.06a
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• pp.79-97
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• 1996

• Journal of the Korean Data and Information Science Society
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• v.9 no.2
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• pp.149-158
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• 1998

In this paper we suggest the joint model of death times and counts with covariates. We assume that the death times follow a Weibull distribution with rate that depends on covariates. For the counts, a Poisson process is assumed with the intensity depending on time and the covariates. We obtain the maximum likelihood estimators of model parameters. This model is applied to data set of patients with breast cancer who received a bone marrow transplant.

• Journal of Veterinary Clinics
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• v.16 no.1
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• pp.80-85
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• 1999

Malassezia(Pityrosoprum) pachydermatis에 의한 피부염의 위험요인을 파악하고자 1997년 1월에서 1998년 12월까지 서울대학교 수의과대학 부속동물병원에 내원하여 본 질환으로 진단된 29두와 동일한 기간 동안 피부과 검사에서 임상적으로 건강한 개로 확인된 97 두의 대조군을 대상으로 분석하였다. 각 설명변수에 대한 교차비(odds ratio, OR)와 신뢰구간(confidence interval, CI)은 변수보정법을 사용하여 계산하였다. 다른 공변수를 보정한 상태에서 다중 로지스틱 회귀분석(multiple logistic regression analysis)을 시행한 결과 피부병기왕력(p=0.0059; OR, 4.44; CI, 1.5∼12.8)과 비만(p=0.0013; OR, 5.38; CI, 1.9∼14.9)은 유의한 위험요인으로 나타났다. 단변량 분석(univariate analysis)에서 주 사료로 고기를 섭취하는 경우 피부염의 위험이 높은 변수로 작용하였지만(p=0.0398; OR, 6.38; CI, 1.1∼37.3) 다른 공변수를 보정한 분석에서는 유의하지 않은 것으로 나타났다. 성별, 품종, 및 예방접종은 위험요인으로 작용하지 않았다.

• Korean Journal of Logic
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• v.12 no.2
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• pp.171-199
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• 2009

This essay will consider evolutionary views that attempt to capture the continuity of theory-change from Newtonian to Einsteinian physics via the formal aspects of these theories. Although it cannot be denied that the formal aspects such as 'correspondence principles' and 'covariance principles' provide important information concerning this theory-change, these formal properties are not sufficient to capture the essential elements of any evolutionary account of the development of Einstein's special and general theories of relativity from Newtonian mechanics.

• Journal of the Korean Home Economics Association
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• v.36 no.11
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• pp.193-207
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• 1998

이 연구의 목적은 아동의 연령과 성에 따른 아동의 역량지각 발달의 경향을 조사하고, 연령, 성을 포함한 가정환경과 또래 환경의 변수들의 역량지각에 미치는 영향을 구조평형 모델을 통해 알아 보았다. 또한, 이러한 역량지각의 발달 성향을 서구 문화권과 비교하여, 역량지각발달의 문화적 보편성이나 차이점을 알아 보고자 하였다. 유아, 또는 초등학교 저학년 아동은 면접으로, 그리고 3학년이상은 설문지를 사용하였다. 조사 대상은 유아, 초등학교 1, 3, 5학년, 중학교 1학년 아동 750명과 그들의 어머니이다. 인지, 사회, 신체 영역에서 모두 역량지각은 연령이 증가할수록 낮아졌다. 인지, 신체 영역의 역량지각에선 연령과 성의 상호작용효과가 나타났다. 그러나, 서구 문화권의 연구에서는 이러한 상호작용이 발견되지 않는다. 역량지각의 공변량구조모형에서는 또래환경 변수가 모두 포함시키기에 부적합한 변수로 나타났고, 연령, 성과 가족의 수입, 아버지의 교육수준, 가정의 물리적 환경, 부모의 정서적 지지가 아동의 역량지각에 의미 있게 영향을 미치는 것으로 나타났다.

• The Korean Journal of Applied Statistics
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• v.24 no.2
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• pp.269-278
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• 2011

There are many researches that have considered the distribution functions and appropriate covariates corresponding to the scores in order to improve the accuracy of a diagnostic test, including the ROC curve that is represented with the relations of the sensitivity and the specificity. The ROC analysis was used by the regression model including some covariates under the assumptions that its distribution function is known or estimable. In this work, we consider a general situation that both the distribution function and the elects of covariates are unknown. For the ROC analysis, the mixtures of normal distributions are used to estimate the distribution function fitted to the credit evaluation data that is consisted of the score random variable and two sub-populations of parameters. The AUC measure is explored to compare with the nonparametric and empirical ROC curve. We conclude that the method using normal mixtures is fitted to the classical one better than other methods.

• Journal of The Korean Association For Science Education
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• v.19 no.2
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• pp.229-238
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• 1999

This study investigated the influences of Vee diagram and regulative metacognitive learning strategies upon 6th-graders' achievement, difficulty toward science lesson, self-efficacy, and learning approach. The Vee diagram and regulative metacognitive learning strategies were modified in a pilot study. Before instruction, an achievement test was administered, and its score was used as a blocking variable. A previous science grade was used as a covariate for post-achievement. Tests of difficulty toward science lesson, self-efficacy, and learning approach were also administered, and the test scores were used as covariates. After instruction, a researcher-made achievement test and post-tests of the above variables were administrated. Two-way ANCOVA results revealed that although there were no significant differences in the achievement test scores, the application subtest scores of the two treatment groups were significantly higher than those of the control group. There were no significant differences in the difficulty toward science lesson and learning approach, but self-efficacy scores for the students with Vee diagram and regulative metacognitive learning strategies were significantly higher than those of the other groups. The perceptions of the students using Vee diagram were also analyzed.

• Journal of Educational Research in Mathematics
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• v.23 no.4
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• pp.505-516
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• 2013

The purpose of this paper is to analyse the essence of proportional reasoning and to analyse the contents of the textbooks according to the mathematics curriculum revised in 2007, and to seek the direction for developing the proportional reasoning in the elementary school mathematics focused the task variables. As a result of analysis, it is found out that proportional reasoning is one form of qualitative and quantitative reasoning which is related to ratio, rate, proportion and involves a sense of covariation, multiple comparison. Mathematics textbooks according to the mathematics curriculum revised in 2007 are mainly examined by the characteristics of the proportional reasoning. It is found out that some tasks related the proportional reasoning were decreased and deleted and were numerically and algorithmically approached. It should be recognized that mechanical methods, such as the cross-product algorithm, for solving proportions do not develop proportional reasoning and should be required to provide tasks in a wide range of context including visual models.

• Journal of the Korean Chemical Society
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• v.46 no.4
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• pp.377-384
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• 2002

In this study, the effect of cooperative computer-assisted instruction upon students' conceptual under-standing,application ability, and learning motivation were investigated by a previous achievement level. The treatment and the control groups (2 classes) were selected from a middle school in Seoul, and taught about the motion of molecule for 5 class periods. Prior to the instructions, a learning motivation test was administered and used as covariate. The scores of a previous achievement test were also used as covariate. The scores of the mid-term science examination were used as blocking variable. After the instructions, the conceptions test, the application test, and the learning motivation test were administered. Two-way ANCOVA results revealed that there were no significant differences in the scores of the con-ceptions test and the application test. However, the scores of the treatment group were found to be significantly higher than those of the control group in the learning motivation test.