• Title/Summary/Keyword: Choice factor

Search Result 780, Processing Time 0.035 seconds

The Effect of Office Workers' Motivation to Choose Clothing and Makeup Colors on Appearance Satisfaction and Self-esteem (직장인의 의복·메이크업 컬러 선택 동기가 외모 만족도와 자아존중감에 미치는 영향)

  • Jeong-Hyun Lee;Seung-Hee Han
    • Journal of the Korean Applied Science and Technology
    • /
    • v.40 no.6
    • /
    • pp.1225-1237
    • /
    • 2023
  • The purpose of this study is to find out the effect of office workers' motivation to choose clothing and makeup colors on appearance satisfaction and self-esteem. The subjects of this study were working women working in Chungcheong-do for two weeks from July 15, 2023 to July 29, 2023, and 696 sampled copies were used for the final analysis. Frequency analysis, factor analysis, reliability analysis, (one-way)ANOVA, and post-verification (Scheffe's) were handled using the SPSS 26.0 program, and office workers' clothing. Correlation analysis, simple regression, and multiple regression were performed to find out the correlation between makeup color selection motivation, and the statistical significance level was p<.I set it to 05. Through this research procedure, the following conclusions were drawn. First, it was found that the motivation of office workers to choose clothes color had a positive (+) effect on appearance satisfaction. Second, office workers' motivation for choosing makeup colors was found to have a positive (+) effect on appearance satisfaction, and physical attractiveness was found to have a positive (+) effect on situational factors. Third, it was found that the color choice of clothes of office workers had a positive (+) effect on self-esteem. Fourth, It was found that the motivation of office workers to choose makeup colors had a positive (+) effect on self-esteem.

Scientifically Gifted Students' Views on the Nature of Science (과학영재들의 과학의 본성에 대한 인식)

  • Kim, Kyoung-Dae;Kang, Soon-Min;Lim, Jai-Hang
    • Journal of The Korean Association For Science Education
    • /
    • v.26 no.6
    • /
    • pp.743-752
    • /
    • 2006
  • The purpose of this study is to gain an understanding of scientifically gifted students' views on the nature of science. A multiple-choice format questionnaire was administered to 237 Korean 10th, 11th and 12th graders at the Korea Science Academy. The differences and similarities by gender and experience of R&E program on the students' views of the nature of science were investigated. The questionnaire developed by Lim(2004) was implemented for this investigation. We found that the majority of scientifically gifted students had highly possessed the tentativeness of scientific knowledge. The students who experienced R&E program have relatively high apprehension of scientists' motivation for researches and activities in social context compared to the students who did not experience an R&E program. Scientifically gifted students had relatively high apprehension that government should not control researches of scientists and relatively low apprehension of social responsibilities of scientists comparing to general high school students. The experience on R&E program was identified as a factor to effect changes in the students' views on the nature of science. The study has implications for the development of gifted program and curriculum such as running and assessing R&E program, and also the pre-service preparation of science teacher, teacher education reformat in both the practical and the policy levels.

The Effect of the Gap between College Students' Perception of the Importance of Coffee Shops and Their Satisfaction after Patronizing Coffee Shops on Their Purchasing Behavior (대전원교학생대가배점중요성적감지화타문광고가배점지후적만의도지간적차거대타문구매행위적영향(大专院校学生对咖啡店重要性的感知和他们光顾咖啡店之后的满意度之间的差距对他们购买行为的影响))

  • Lee, Won-Ok
    • Journal of Global Scholars of Marketing Science
    • /
    • v.19 no.4
    • /
    • pp.1-10
    • /
    • 2009
  • The purpose of this study was to categorize the gap between coffee shop 'importance' (as perceived by customers before patronizing the coffee shop) and 'satisfaction' (perception of customers after patronizing the coffee shop) as positive or negative and to analyze the effect of these gaps on purchasing behavior. To do this, I used the gap between importance and satisfaction regarding the choice of a coffee shop as the explanatory variable and performed an empirical analysis of the direction and size of the effect of the gap on purchasing behavior (overall satisfaction, willingness-to-revisit) by applying the Ordered Probit Model (OPM). A previous study that used IPA to evaluate the effects of gaps estimated the direction and size of a quadrant but failed to analyze the effect of gaps on customers. In this study, I evaluated the effects of positive and negative gaps on customer satisfaction and willingness-to-revisit. Using OPM, I quantified the effect of positive and negative gaps on overall customer satisfaction and willingness-to-revisit. Per-head expenditure, frequency of visits, and coffee-purchasing place had the most positive effects on overall customer satisfaction. Frequency of visits, followed by per-head expenditure and then coffee-purchasing place, had the most positive impact on willingness-to-visit. Thus per-head expenditure and frequency of visits had the greatest positive effects on overall satisfaction and willingness-to-revisit. This finding implies that the higher the actual satisfaction (gap) of customers who spend KRW5,000 or more once or more per week at coffee shops is, the higher their overall satisfaction and willingness-to-revisit are. Despite the fact that economical efficiency had a significant effect on overall satisfaction and willingness-to-revisit, college and university students still use coffee shops and are willing to spend KRW5,000 because they do not only purchase coffee as a product itself, but use the coffee shop for other activities, such as working, meeting friends, or relaxing. College and university students also access the Internet in coffee shops via personal laptops, watch movies, and study; thus, coffee shops should provide their customers with the appropriate facilities and services. The fact that a positive gap for coffee shop brand had a positive effect on willingness-to-revisit implies that the higher the level of customer satisfaction, the greater the willingness-to-revisit. A negative gap for this factor, on the other hand, implies that the lower the level of customer satisfaction, the lower the willingness-to-revisit. Thus, the brand factor has a comparatively greater effect on satisfaction than the other factors evaluated in this study. Given that the domestic coffee culture is becoming more upscale and college/university students are sensitive to this trend, students are attentive to brands. In most upscale coffee shops in Korea, the outer wall is built out of glass that can be opened, the interiors are exotic with an open kitchen. These upscale coffee shops function as landmarks and match the taste of college/university students. Coffee shops in Korea have become a cultural brand. To make customers feel that coffee shops are upscale, good quality establishments and measures to provide better services in terms of brand factor should be instituted. The intensified competition among coffee shop brands in Korea as a result of the booming industry indicates that provision of additional services is needed to differentiate competitors. These customers can also use a scanner free of charge. Another strategy that can be used to boost brands could be to provide and operate a seminar room for seminars and group study. If coffee shops adopt these types of strategies, college/university students would be more likely to consider the expenses they incur worthwhile and, subsequently, they would be more likely to be satisfied with the brands of these coffee shops, with an associated increase in their willingness-to-revisit. Gender and study year had the most negative effects on overall satisfaction and willingness-to-revisit. Female students were more likely to be satisfied and be willing to return than male students, and third and fourth-year students were more likely to be satisfied and willing-to-return than first or second-year students. Students who drink coffee, read books, and use laptops alone at coffee shops are easily noticeable. High-grade students tend to visit coffee shops alone in order to use their time efficiently for self-development and to find jobs. The economical efficiency factor had the greatest effect on overall satisfaction and willingness-to-revisit in terms of a positive gap. The higher the actual satisfaction (gap) of students with the price of the coffee, the greater their overall satisfaction and willingness-to-revisit. Economical efficiency with a negative gap had a negative effect on willingness-to-revisit, which implies that a less negative gap will result in a greater willingness-to-revisit. Amid worsening market conditions, coffee shops located around colleges/universities are using strategies, such as a point or membership card, strategic alliances with credit-card companies, development of a set menu or seasonal menu, and free coffee-shot services to increase their competitive edge. Product power also had a negative effect in terms of a negative gap, which indicates that a higher negative gap will result in a lower willingness-to-revisit. Because there are many more customers that enjoy coffee in this decade, as compared to previous decades, the new generation of customers, namely college/university students, want various menu items in addition to coffee, and coffee shops should, therefore, add side menu items, such as waffles, rice cakes, cakes, sandwiches, and salads. For example, Starbucks Korea is making efforts to enhance product power by selling rice cakes flavored in strawberry, wormwood, and pumpkin, and providing coffee or cream free of charge. In summary, coffee shops should focus on increasing their economical efficiency, brand, and product power to enhance the satisfaction of college/university students. Because shops adjacent to colleges or universities enjoy a locational advantage, providing differentiated services in terms of economical efficiency, brand, and product power, is likely to increase customer satisfaction and return visits. Coffee shop brands should, therefore, be innovative and embrace change to meet their customers' desires. Because this study only targeted college/university students in Seoul, comparative studies targeting diverse regions and age groups are required to generalize the findings and recommendations of this study.

  • PDF

Dosimetric Characteristics of Detectors in Measurement of Beam Data for Small Fields of Linear Accelerator (선형가속기의 소조사면에 대한 빔 자료 측정에서 검출기의 선량 특성 분석)

  • Koo, Ki-Lae;Yang, Oh-Nam;Lim, Cheong-Hwan;Choi, Won-Sik;Shin, Seong-Soo;Ahn, Woo-Sang
    • Journal of radiological science and technology
    • /
    • v.35 no.3
    • /
    • pp.265-273
    • /
    • 2012
  • Aquisition of accurate beam data is very important to calculate a reliable dose distribution of the treatment planning system for small radiation fields in intensity-modulated radiation therapy(IMRT) and stereotactic radiosurgery(SRS). For the measurement of small fields, the choice of a suitable detector is important due to the shape gradient in profile penumbra, the lack of lateral electronic equilibrium, and the effect of effective detector volume. Therefore, this study was to analyze the dosimetric characteristics of various detectors in measurement of beam data for small fields of linear accelerator. 0.01cc and 0.13cc ion chambers (CC01 and CC13) and a stereotactic diode detector(SFD) were used for measurement of small fields. The beam data, including the percent depth dose, output factor, and beam profile were acquired under 6 MV and 15 MV photon beams. Measurements were performed with the field size ranging from $2{\times}2cm^2$ to $5{\times}5cm^2$. For $2{\times}2cm^2$ field size, the differences of the ratios of $PDD_{20}$ and $PDD_{10}$ measured by CC01 and SFD detectors were 1.02% and 0.12% for 6 MV and 15 MV photon beams, respectively. For field sizes larger than $3{\times}3cm^2$, the differences of values of $PDD_{20}/PDD_{10}$ obtained from each detector were 1.15% and 0.71% for 6 MV and 15 MV photon beams, respectively. The output factors obtained from CC01 and SFD for $2{\times}2cm^2$ field size were within 0.5% and 1.5% for 6 MV and 15 MV, respectively. The differences in output factor of three detectors for $3{\times}3cm^2$ to $5{\times}5cm^2$ field sizes were within 0.5%. Profile penumbras measured by the SFD, CC01, and CC13 detectors at three depths were average 2.7 mm and 3.5 mm, 3.4 mm and 4.3 mm, and 5.2 mm and 6.1 mm for 6 MV and 15 MV photon beams, respectively. In conclusion, it could be possible to use of the CC01 and SFD detectors for the measurement of percent depth dose and output factor for $2{\times}2cm^2$ field size, and to use of three detectors for $3{\times}3cm^2$ to $5{\times}5cm^2$ field sizes. CC01 and SFD detectors, consider ably smaller than the radiation field, should be used in order to accurately measure the profile penumbra for small field sizes.

The Effect of E-SERVQUAL on e-Loyalty for Apparel Online Shopping (재망상복장구물중전자(在网上服装购物中电子)E-SERVQUAL 대전자충성도적영향(对电子忠诚度的影响))

  • Kim, Eun-Young;Jackson, Vanessa P.
    • Journal of Global Scholars of Marketing Science
    • /
    • v.19 no.4
    • /
    • pp.57-63
    • /
    • 2009
  • With an exponential increase in electronic commerce (e-commerce), marketers are attempting to gain a competitive advantage by emphasizing service quality and post interaction service aspects, which leads to customer satisfaction or behavioral consequence. Particularly for apparel, service quality is one of the key determinants in encouraging customer e-loyalty, and hence the success of apparel retailing in the context of electronic commerce. Therefore, this study explores e-service quality (E-SERVQUAL) factors and their unique effects on e-loyalty for apparel online shopping based on Parasuraman et al' s (2005) framework. Specific objectives of this study are to identify underlying dimension of E-SERVQUAL, and analyze a structural model for examining the effect of E-SERVQUAL on e-loyalty for online apparel shopping. For the theoretical framework of service quality in the context of online shopping, literatures on traditional and electronic service quality factors were comparatively reviewed, and two aspects of core and recovery services were identified. This study hypothesized that E-SERVQUAL has an effect on e-loyalty; customer satisfaction has a positive effect on e-service loyalty for apparel online shopping; and customer satisfaction mediates in the effect of E-SERVQUAL on e-loyalty for apparel online shopping. A self-administered questionnaire was developed based on literatures. A total of 252 usable questionnaires were obtained from online consumers who had purchase experience with online shopping for apparel products and reside in standard metropolitan areas, in the United States. Factor analysis (e.g., exploratory, confirmatory) was conducted to assess the validity and reliability and the structural equation model including measurement and structural models was estimated via LISREL 8.8 program. Findings showed that the E-SERVQUAL of shopping websites for apparel consisted of five factors: Compensation, Fulfillment, Efficiency, System Availability, and Responsiveness. This supports Parasuraman (2005)'s E-S-QUAL encompassing two aspects of core service (e.g., fulfillment, efficiency, system availability) and recovery related service (e.g., compensation, responsiveness) in the context of apparel shopping online. In the structural equation model, there are five exogenous latent variables for e-SERVQUAL factors; and two endogenous latent variables (e.g., customer satisfaction, e-loyalty). For the measurement model, the factor loadings for each respective construct were statistically significant and were greater than .60 and internal consistency reliabilities ranged from .85 to .88. In the estimated structural model of the e-SERVEQUAL factors, the system availability was found to have direct and positive effect on e-loyalty, whereas efficiency had a negative effect on e-loyalty for apparel online shopping. However, fulfillment was not a significant predictor for explaining consequences of E-SERVQUAL for apparel online shopping. This finding implies that perceived service quality of system available was likely to increase customer satisfaction for apparel online shopping. However, it was not supported that e-loyalty was determined by service quality, because service quality has an indirect effect on e-loyalty (i.e., repurchase intention) by mediating effect of value or satisfaction in the context of online shopping for apparel. In addition, both compensation and responsiveness were found to have a significant impact on customer satisfaction, which influenced e-loyalty for apparel online shopping. Thus, there was significant indirect effect of compensation and responsiveness on e-loyalty. This suggests that the recovery-specific service factors play an important role in maximizing customer satisfaction levels and then maintaining customer loyalty to the online shopping site for apparel. The findings have both managerial and research implications. Fashion marketers can establish long-term relationship with their customers based on continuously measuring customer perceptions for recovery-related service quality, such as quick responses to problem and returns, and compensation for customers' problem after their purchases. In order to maintain e-loyalty, recovery services play an important role in the first choice websites for consumers to purchase clothing. Given that online consumers may shop anywhere, a marketing strategy for improving competitive advantages is to provide better service quality, maximize satisfaction, and turn to creating customers' e-loyalty for apparel online shopping. From a researcher's perspective, there are some limitations of this research that should be considered when interpreting its findings. For future research, findings provide a basis for the further study of this important topic along both theoretical and empirical dimensions. Based on the findings, more comprehensive models for predicting E-SERVQUAL's consequences can be developed and tested. For global fashion marketing, this study can expand to a cross-cultural approach into e-service quality for apparel by including multinational samples.

  • PDF

A Study on the Determinants of Perceived Social Usefulness and Continuous Use Intention of the Internet of things in the Public Sector (공공부문 사물인터넷의 지각된 사회적 유용성 및 지속사용의도 향상을 위한 결정요인에 관한 연구)

  • Yoon, Seong-Jeong;Kim, Min-Yong
    • Management & Information Systems Review
    • /
    • v.36 no.1
    • /
    • pp.115-141
    • /
    • 2017
  • This study is to find the key factors of the Internet of Things for development in public sector. In previous studies, it is said that Internet of Things can work digital system without human operation and gives a lot of outputs(information) users. Generally, people are a subject of operating digital system in traditional way, while people are an object on the internet of things. In other words, it is possible to work digital system with only networking from things to things. After all, it is reported that these advantages of the Internet of Things make possible to reduce social costs significantly in public sector. However, despite the strengths of the Internet of Things, there is a specific user acceptance of the technology factor for the Internet of Things rarely. It means that developing of the Internet of Things only focuses on the final purpose. If the focus on development meet this purpose, the user is ignored for the specific reason that using a technique. As a result of this, many users gradually decrease the continuous using of the Internet of Things. Thus, in this study, we need to find what critical factors should reflect to the Internet of Things in public sector. To find this result, there is no choice to use Technology Acceptance Model(TAM). Many researchers have proved that Technology Acceptance Model is valid through the four process in model introduction, confirmation, expansion and refinement from 1986 to 2003. The results of this study showed that the result explanatory power of Internet of Things in public sector is the most important factor affecting only perceived social usefulness and ease of use. Finally, it can be seen that the user has a positive attitude toward use, which has a positive effect on the intention to use continuously. The implications of this study are summarized as follows: When the public Internet of Things service is provided, it means that the user can easily understand the result, and when the person and the object communicate the result to each other, they should be able to communicate with each other. This means that a lot of user effort is needed to understand the outcome of the public Internet of Things being provided.

  • PDF

Coronary Artery Bypass Graft Surgery in the Elderly (고령환자의 관상동맥 우회로 조성술)

  • 김학제;황재준;김현구;신재승;손영상;최영호
    • Journal of Chest Surgery
    • /
    • v.32 no.8
    • /
    • pp.715-721
    • /
    • 1999
  • Background:The number of old patients receiving coronary artery bypass grafting(CABG) is increasing. With the more recent advances in operative techniques, the age at which CABG is indicated has also increased. This study evaluated the risk factors associated with the hospital mortality and the morbidity following CABG in elderly patients. Material and Method: Between March 1991 and June 1998, we retrospectively reviewed 45 consecutive patients aged 65 years or older who underwent CABG. We compared the data with the results of 179 patients under the age 65 years operated during the same period. Result: Mean age was 68${\pm}$1.41 years(range 65 to 74 years). Emergency surgery was required in 4, and elective surgery in 41 patients. The mean number of distal anastomosis per patient was 3.62 ${\pm}$0.81 and mean aortic cross-cramp time was 69.84${\pm}$18.5 minutes. Thirty patients had Canadian class III or IV preoperatively, but 43 patients had class I or II postoperatively. The left ventricular ejection fraction increased significantly from 54.23${\pm}$10.62% preoperatively to 58.14${\pm}$9.88% postoperatively(p<0.05). Postoperative complication was pneumonia in 2 patients, acute renal failure in 2 patients, sternal wound infection in 1 patient, and postoperative myocardial infarction in 1 patient. There were two postoperative deaths. The causes of deaths were low output syndrome in one patient, and sepsis due to pneumonia in the other patient. The hospital mortality was higher in the elderly group(4.4 versus 2.86%) but was not statistically significant(p>0.05). Incremental risk factors for hospital deaths in the elderly were emergent operation, preoperative PTCA, postoperative use of IABP and postoperative ARF(p<0.05). The duration of hospital stay after operation was significantly longer for the elderly group than the younger group(19.27${\pm}$12.51 vs 15.55${\pm}$6.99 days; p< 0.05). Follow-up was complete for 34 of the hospital survivors and ranged from 1 to 73 months(mean: 23.58${\pm}$19.56 months). There was no late mortality of cardiac origin. Conclusion: Age is an important factor in selecting optimal management for elderly patients with coronary compromise, but age alone should not dictate the choice of therapy. Coronary artery bypass surgery in the elderly is associated with acceptable early mortality and excellent long-term results.

  • PDF

An Ethnographic Study about Taegyo Practice in Korea (태교 실천에 대한 일상생활 기술적 연구)

  • 김현옥
    • Journal of Korean Academy of Nursing
    • /
    • v.27 no.2
    • /
    • pp.411-422
    • /
    • 1997
  • The purpose of this study is twofold : (i) to investigate how much effort the married couples are making for the good health of both the pregnant woman and her unborn child from the time of their marriage to and during the period of conception : and (ii) to comprehensive investigate socio-cultural back-grounds which affect prenatal effort. Result of this study provide a basis for the prenatal care program which will be appropriate to our culture. This study has been done by the ethnographic research method. The subjects of this study are 53 people in all consisting of 33 pregnant women and 20 husbands. In order to investigate socio-cultural factors which influence Taegyo, producers of Taegyo music were interviewed. In addition the researcher surveyed the markets of Taegyo music, participated in special courses of prenatal education, analyzed the content of the books and periodicals dealing with Taegyo, and collected the concept of Taegyo distributed by the mass media. The full-fledged study continued for eight months from February to August.1996. The data were analyzed as soon as they were collected. Spradly's(1979, 1980) developmental, sequential method of domain analysis. taxonomic analysis, componential analysis, and theme analysis in this order was adopted as the procedure of analyzing the data. To obtain the exactness of study, Sandelowski's (1986) four criteria, that is, Credibility, Fittingness, Auditability, and Confirmability were applied to all stages of data collection, data analysis, the interpretation of the result, and the description of the result. The following are the result : 1. The couples' Taegyo at the stage of preconception was related to their physical, psychological, spiritual conditions under which a healthy baby will be born. Specific methods they prefer are : "the choice of one's spouse." "physical check-up," "physical good health, " "praying, " and so on. 2. When the marriod couple have sex in order to conceive, their Taegyo was related to the imposition of their physical, psychological, and environmental conditions. Specific methods they prefer are : "having sex at specific time, " "having sex in nice place." "to purify their minds while having sex," and so on. 3. The married couples' Taegyo while they are in pregnancy was related to the imposition of their physical. psychological, emotionmental. environmental, social and spiritual conditions. Specific methods they prefer are : "listening to music. " "reading," "looking at beautiful things only," "to avoid looking at or listening to bad things." "to eat food in good shape, " "to avoid drugs," "eating Korean herbal medicine." "sexual abstinence," "to avoid dangerous places," "to keep emotional tranquility," "moderate exercises and rest." "leading a pure life." "praying." "being aware of their words and behavior." "for the couple to keep a good relationship." "interaction with their unborn child," "to support Taegyo for pregnant women," and so on. 4. The married couple put Taegyo into practice on the basis of the following principles : the principle of respecting an unborn child, the principle of forming a good disposition. the principle of top-down parental love, the principle of synergy between a pregnant woman and her unborn child, the principle of expecting a good child, the principle of forming a good habit, and the principle of acquiring a parental role. 5. The practice of Taegyo is influenced by such factors as the married couple, the supporting system, and the mass media. As the husband -and-wife factor, their information of Taegyo, the degree of importance is assigned to their characters, their time to spare, their healthiness, the age of pregnant woman, their conception plan, their religion, their belief of the Taegyo effects, and the birth of a baby in this order. The factor of the supporting system consists of her husband's support, her family support, and her neighbor's support. The mass media factors include the broadcasting media, books specialized in Taegyo, periodicals for pregnant women, booklets for advertizing powdered milk, Taegyo music of record manufacturing companies, and the teaching materials for gifted children. Among these the mass media is especially taking advantage of Taegyo as its main source of economic profits are leading the public behavior pattern to a prodigal one. Taegyo is a self-control behavior which requires practice for the following : the physical and psychological good health of the pregnant woman and her unborn child, the development of the unborn child's good character, the development of the unborn child's intelligence and talents, the expectation of the unborn child's good features. shape a good habit, the expectation of the unborn child's bright future, and the learning of a parental role, the expectation of male birth. Above all it is a type of our good cultural tradition which pursues a value higher than the one that the prenatal care does. The principles of pregnancy care inherent in the habit of Taegyo will provide us a guideline for the development of the prenatal care.

  • PDF

Optimal Selection of Classifier Ensemble Using Genetic Algorithms (유전자 알고리즘을 이용한 분류자 앙상블의 최적 선택)

  • Kim, Myung-Jong
    • Journal of Intelligence and Information Systems
    • /
    • v.16 no.4
    • /
    • pp.99-112
    • /
    • 2010
  • Ensemble learning is a method for improving the performance of classification and prediction algorithms. It is a method for finding a highly accurateclassifier on the training set by constructing and combining an ensemble of weak classifiers, each of which needs only to be moderately accurate on the training set. Ensemble learning has received considerable attention from machine learning and artificial intelligence fields because of its remarkable performance improvement and flexible integration with the traditional learning algorithms such as decision tree (DT), neural networks (NN), and SVM, etc. In those researches, all of DT ensemble studies have demonstrated impressive improvements in the generalization behavior of DT, while NN and SVM ensemble studies have not shown remarkable performance as shown in DT ensembles. Recently, several works have reported that the performance of ensemble can be degraded where multiple classifiers of an ensemble are highly correlated with, and thereby result in multicollinearity problem, which leads to performance degradation of the ensemble. They have also proposed the differentiated learning strategies to cope with performance degradation problem. Hansen and Salamon (1990) insisted that it is necessary and sufficient for the performance enhancement of an ensemble that the ensemble should contain diverse classifiers. Breiman (1996) explored that ensemble learning can increase the performance of unstable learning algorithms, but does not show remarkable performance improvement on stable learning algorithms. Unstable learning algorithms such as decision tree learners are sensitive to the change of the training data, and thus small changes in the training data can yield large changes in the generated classifiers. Therefore, ensemble with unstable learning algorithms can guarantee some diversity among the classifiers. To the contrary, stable learning algorithms such as NN and SVM generate similar classifiers in spite of small changes of the training data, and thus the correlation among the resulting classifiers is very high. This high correlation results in multicollinearity problem, which leads to performance degradation of the ensemble. Kim,s work (2009) showedthe performance comparison in bankruptcy prediction on Korea firms using tradition prediction algorithms such as NN, DT, and SVM. It reports that stable learning algorithms such as NN and SVM have higher predictability than the unstable DT. Meanwhile, with respect to their ensemble learning, DT ensemble shows the more improved performance than NN and SVM ensemble. Further analysis with variance inflation factor (VIF) analysis empirically proves that performance degradation of ensemble is due to multicollinearity problem. It also proposes that optimization of ensemble is needed to cope with such a problem. This paper proposes a hybrid system for coverage optimization of NN ensemble (CO-NN) in order to improve the performance of NN ensemble. Coverage optimization is a technique of choosing a sub-ensemble from an original ensemble to guarantee the diversity of classifiers in coverage optimization process. CO-NN uses GA which has been widely used for various optimization problems to deal with the coverage optimization problem. The GA chromosomes for the coverage optimization are encoded into binary strings, each bit of which indicates individual classifier. The fitness function is defined as maximization of error reduction and a constraint of variance inflation factor (VIF), which is one of the generally used methods to measure multicollinearity, is added to insure the diversity of classifiers by removing high correlation among the classifiers. We use Microsoft Excel and the GAs software package called Evolver. Experiments on company failure prediction have shown that CO-NN is effectively applied in the stable performance enhancement of NNensembles through the choice of classifiers by considering the correlations of the ensemble. The classifiers which have the potential multicollinearity problem are removed by the coverage optimization process of CO-NN and thereby CO-NN has shown higher performance than a single NN classifier and NN ensemble at 1% significance level, and DT ensemble at 5% significance level. However, there remain further research issues. First, decision optimization process to find optimal combination function should be considered in further research. Secondly, various learning strategies to deal with data noise should be introduced in more advanced further researches in the future.

Technical Inefficiency in Korea's Manufacturing Industries (한국(韓國) 제조업(製造業)의 기술적(技術的) 효율성(效率性) : 산업별(産業別) 기술적(技術的) 효율성(效率性)의 추정(推定))

  • Yoo, Seong-min;Lee, In-chan
    • KDI Journal of Economic Policy
    • /
    • v.12 no.2
    • /
    • pp.51-79
    • /
    • 1990
  • Research on technical efficiency, an important dimension of market performance, had received little attention until recently by most industrial organization empiricists, the reason being that traditional microeconomic theory simply assumed away any form of inefficiency in production. Recently, however, an increasing number of research efforts have been conducted to answer questions such as: To what extent do technical ineffciencies exist in the production activities of firms and plants? What are the factors accounting for the level of inefficiency found and those explaining the interindustry difference in technical inefficiency? Are there any significant international differences in the levels of technical efficiency and, if so, how can we reconcile these results with the observed pattern of international trade, etc? As the first in a series of studies on the technical efficiency of Korea's manufacturing industries, this paper attempts to answer some of these questions. Since the estimation of technical efficiency requires the use of plant-level data for each of the five-digit KSIC industries available from the Census of Manufactures, one may consture the findings of this paper as empirical evidence of technical efficiency in Korea's manufacturing industries at the most disaggregated level. We start by clarifying the relationship among the various concepts of efficiency-allocative effciency, factor-price efficiency, technical efficiency, Leibenstein's X-efficiency, and scale efficiency. It then becomes clear that unless certain ceteris paribus assumptions are satisfied, our estimates of technical inefficiency are in fact related to factor price inefficiency as well. The empirical model employed is, what is called, a stochastic frontier production function which divides the stochastic term into two different components-one with a symmetric distribution for pure white noise and the other for technical inefficiency with an asymmetric distribution. A translog production function is assumed for the functional relationship between inputs and output, and was estimated by the corrected ordinary least squares method. The second and third sample moments of the regression residuals are then used to yield estimates of four different types of measures for technical (in) efficiency. The entire range of manufacturing industries can be divided into two groups, depending on whether or not the distribution of estimated regression residuals allows a successful estimation of technical efficiency. The regression equation employing value added as the dependent variable gives a greater number of "successful" industries than the one using gross output. The correlation among estimates of the different measures of efficiency appears to be high, while the estimates of efficiency based on different regression equations seem almost uncorrelated. Thus, in the subsequent analysis of the determinants of interindustry variations in technical efficiency, the choice of the regression equation in the previous stage will affect the outcome significantly.

  • PDF