• Journal of Korean Society of Forest Science
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• v.98 no.2
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• pp.148-155
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• 2009

The objective of this study is to know market structures of softwood logs being imported to South Korea from log producing countries. Import demand of softwood logs imported to South Korea from America, New Zealand and Chile is fixed as a function of log prices, the lagged dependent variable and output. On the basis of the adaptive expectations model, linear regression models that the explanatory variables included and the lagged dependent variable were estimated by Seemingly Unrelated Regression Equations (SURE). The short-run and long-run own price elasticity of America's softwood log import demand is -1.738 and -4.250 respectively. Then long-run elasticity is much higher than short-run elasticity. Short-run and long-run crosselasticity of New Zealand's softwood log import demand with respect to American's softwood log import price are inelastic at 0.505 and 0.883 respectively. Short-run and long-run cross-elasticity of Chile's softwood log import demands with respect to American's softwood log import prices were highly elastic at 2.442 and 4.462 respectively. Long-run elasticity was almost twice as high as short-run elasticity.

• Proceedings of the Korean Institute of Intelligent Systems Conference
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• 2003.09a
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• pp.431-434
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• 2003

In this paper we introduce a modified objective function for fuzzy c-means clustering with logistic regression model in the presence of noise cluster. The logistic regression model is commonly used to describe the effect of one or several explanatory variables on a binary response variable. In real application there is very often no sharp boundary between clusters so that fuzzy clustering is often better suited for the data.

• Journal of the Korean Data and Information Science Society
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• v.15 no.4
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• pp.935-943
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• 2004

Most of the accelerated life tests deal with tests that use only one accelerating variable and no other explanatory variables. Frequently, however, there is a test to use more than one accelerating or other experimental variables, such as, for examples, a test of capacitors at higher than usual conditions of temperature and voltage, a test of circuit boards at higher than usual conditions of temperature, humidity and voltage. A accelerated life test is extended to M-level stress accelerated life test with k-stress variables. The optimal design for Weibull distribution is studied with k-stress variables.

• Communications for Statistical Applications and Methods
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• v.2 no.1
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• pp.74-88
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• 1995

This article introduces a unified method of choosing the most explanatory and significant multiway partitions for classification tree design and analysis. The method is derived on the impurity reduction (IR) measure of divergence, which is proposed to extend the proportional-reduction-in-error (PRE) measure in the decision-theory context. For the method derivation, the IR measure is analyzed to characterize its statistical properties which are used to consistently handle the subjects of feature formation, feature selection, and feature deletion required in the associated classification tree construction. A numerical example is considered to illustrate the proposed approach.

• Journal of dental hygiene science
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• v.5 no.4
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• pp.171-177
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• 2005

This study aims to analyze effects of mothers' socioeconomic features, and knowledge and behavior of oral health on experience and purpose of using dentistry. By survey to 103 mothers of 5-6 year old children, who use day care centers in seoul, the results are obtained as follows: 1. As for the rate of experiencing dental care classified by its purpose, 56.7% for dental treatment, 23.3% for regular check-up and 20.0% for precaution 2. There was no significant difference of correlativity between mothers' socioeconomic features and knowledge of oral health and experience of using dental care, while the lower rate of using dental floss, the higher rate of experiencing dental care(p < 0.01). 3. In respect of correlativity between mother's socioeconomic features and purpose of using dental care, the purpose of regular checkup was high in a group of mothers between 33 and 35 years old(71.4%) by ages and in a group of mothers who graduated from college(57.1%) by academic background(p < 0.05). 4. In correlativity between mothers' behavior of oral health and purpose of using dental care, the result showed that the higher the rate of using dental floss was, the higher the rate of experiencing dental care for a regular check-up was(p < 0.001) and the higher the rate of using fluoride dentifrices was, the higher the rate of using dental care for cure was(p < 0.05). 5. Multiple regression based on dependent variable of experience in using dental care showed that average monthly income(less than 2,500,000 won) was significant explanatory factor with 65% of explanatory variance. On the other hand, multiple regression based on dependent variable of purpose of using dental care showed that vocation(professional job) and age(between 33 and 35 years old) was significant explanatory factor with 70% of explanatory variance for a regular check-up, age(between 33 and 35 years old) and average monthly income (less than 2,500,000 won) was significant factor with 78% of explanatory variance for precaution and age(less than 32 years old) was significant explanatory factor with 33% of explanatory variance for treatment.

• Journal of Labour Economics
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• v.38 no.1
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• pp.1-30
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• 2015

The aggregate matching function is estimated to explain dynamics among job seekers, vacancies and new hires in Korea. Due to measurement errors inherent in vacancies data, I introduce a latent variable for job openings and use the instrumental variables to correct its endogeneity. Matching efficiency is also estimated using some explanatory variables like job seekers' characteristics and public employment services. The result shows that Korea's matching function also exhibits a constant returns to scale.

• Journal of Integrative Natural Science
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• v.8 no.1
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• pp.56-59
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• 2015

To explore effects on each friendship, family, romance, and community in sub-variables of loneliness on academic achievement in science for Y-middle school students, multiple regression analysis is carried out by stepwise method. As the results, I found the following facts. Academic achievement in science for the students was expressed by the following equation. Academic Achievement=48.765+4.012${\times}$[Family](t=2.082, p=.039)-3.957${\times}$[Romance](t=-3.147, p=.002)+5.281${\times}$[Community](t=2.965, p=.003). And each variable value of the explanatory power affecting academic achievement in science for the students is presented in order of community (12.0%), family (6.6%), and romance (6.3%). But the friendship variable is not significant in affecting academic achievement in science.

• Journal of Korean Society of Forest Science
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• v.97 no.2
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• pp.140-143
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• 2008

This study compared the plywood demand prediction accuracy of econometric and vector autoregressive models using Korean data. The econometric model of plywood demand was specified with three explanatory variables; own price, construction permit area, dummy. The vector autoregressive model was specified with lagged endogenous variable, own price, construction permit area and dummy. The dummy variable reflected the abrupt decrease in plywood consumption in the late 1990's. The prediction accuracy was estimated on the basis of Residual Mean Squared Error, Mean Absolute Percentage Error and Theil's Inequality Coefficient. The results showed that the plywood demand prediction can be performed more accurately by econometric model than by vector autoregressive model.

• Journal of Korean Society of Forest Science
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• v.95 no.2
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• pp.203-208
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• 2006

This study compared the roundwood demand prediction accuracy of econometric and time-series models using Korean data. The roundwood was divided into softwood and hardwood by species. The econometric model of roundwood demand was specified with four explanatory variables; own price, substitute price, gross domestic product, dummy. The time-series model was specified with lagged endogenous variable. The dummy variable reflected the abrupt decrease in roundwood demand in the late 1990's in the case of softwood roundwood, and the boom of plywood export in the late 1970's in the case of hardwood roundwood. On the other hand, the prediction accuracy was estimated on the basis of Residual Mean Square Errors(RMSE). The results showed that the softwood roundwood demand prediction can be performed more accurately by econometric model than by time-series model. However, the hardwood roundwood demand prediction accuracy was similar in the case of using econometric and time-series model.

• Journal of the Korean Home Economics Association
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• v.28 no.2
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• pp.57-72
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• 1990

The purpose of this study were ; (1) to analyze the relationship between actual housing condition and housing satisfaction with socio-demographic and housing characteristics of respondents and (2) to present the device on the quality of housing environment in low-income families. The sample was a proportional, stratified, random sample of 299 low-income families in Deajeon. The major findings were as follows: 1) The wholey, actual housing conditions were not good; especially the worst conditions appeared exterior walls, roof, kitchen, bath and toilet, heating, noise, recreation facilities as play-ground. 2) Actual housing condition has been found to be related to income, tenure(rent or own), persons/room. In the relation of the socio-demographic and housing characteristics, actual housing condition, housing satisfaction, income and persons/room were found to be a significant explanatory variable in actual housing condition. And actual housing condition ws appeared to be the strongest variable in housing satisfaction. 3) Housing of the low-income families should be improved physical aspects of the environment and be reflected in need of the occupant that based on the social-welfare housing concept.