• The Korean Journal of Applied Statistics
• /
• v.29 no.2
• /
• pp.301-308
• /
• 2016

The process capability index is used to determine whether a production process is capable of producing items within a specified tolerance. Some process capability indices $C_p$, $C_{pk}$ and $C_{pm}$ have been of particular interest as useful management tools for tracking process performance. Most evaluations on process capability indices focus on statistical estimation and test of hypothesis. It is necessary to investigate their asymptotic correlationship among basic estimators ${\hat{C}}_p$, ${\hat{C}}_{pk}$ and ${\hat{C}}_{pm}$ of process capability indices $C_p$, $C_{pk}$ and $C_{pm}$. In this paper, we study their asymptotic correlationship for three process capability indices ${\hat{C}}_p$, ${\hat{C}}_{pk}$ and ${\hat{C}}_{pm}$ under bivariate normal distribution BN(${\mu}_x,{\mu}_y,{\sigma}^2_x,{\sigma}^2_y,{\rho}$). With some nonnormal processes, the asymptotic correlation coefficient of any two respective process capability index estimators could be established.

• Communications for Statistical Applications and Methods
• /
• v.15 no.3
• /
• pp.451-464
• /
• 2008

Six sigma is the rating that signifies "best in clas", with only 3.4 defects per million units or operations. Higher sigma quality level is generally perceived by customers as improved performance by assigning a correspondingly higher satisfaction score. The process capability indices and the sigma level $Z_{st}$ have been widely used in six sigma industries to assess process performance. Most evaluations on process capability indices focus on point estimates, which may result in unreliable assessments of process performance. In this paper, we consider statistical inference for process capability indices $C_p$, $C_{pk}$ and $C_{pm}$. Also, we study better testing procedure on assessing sigma level $Z_{st}$ and capability index $C_{pm}$, for practitioners to use in determining whether a given process is capable. The proposed method is easy to use and the decision making is more reliable. Whether a process is clearly normal or nonnormal, our bootstrap testing procedure could be applied effectively without the complexity of calculation. A numerical result based on our proposed method is illustrated.

• Journal of Korea Water Resources Association
• /
• v.38 no.8 s.157
• /
• pp.605-616
• /
• 2005

In this paper, runoff curve numbers (CN's) for a small forested mountainous catchment are estimated using rainfall-runoff data measured at Sulma experimental catchment every 10 minutes and a new guideline for applying the antecedent rainfall conditions (ARC's) for small mountainous watersheds in Korea is proposed. Sulma experimental catchment is a typical natural mountainous basin with $97\%$ of forested land cover and CN's are estimated to be in the range between 51 and 89 with median value of 72. The test hypothesis stating as 1-day ARC is better than 5-day ARC in determining CN's for a small mountainous watershed is shown to be acceptable. Also, linear regression equations for the estimation of CN's for small mountainous catchments are proposed. As there is no significant investigations available on CN's for small mountainous catchments, the newly proposed relationships between CN's and ARC may be used as a preliminary guideline to assign CN's for the estimation of floods from rainfall data on mountainous regions.

• Journal of Life Science
• /
• v.21 no.2
• /
• pp.328-333
• /
• 2011

Melatonin has been known as an animal hormone. However, melatonin exists in diverse organisms including higher plants. The biosynthesis and physiological roles for melatonin in plants is still largely unknown, although both dicot and monocot plants have melatonin and some medicinal plants even contain large amounts of melatonin. In this study we detected melatonin in diverse Viola plants, in which melatonin had not been examined so far, by reverse phase HPLC analysis, demonstrating the wide existence of melatonin in the genus of Viola. We then fed tryptophan (Trp) and tryptamine (TAM) to the incubation medium for Viola leaf sections to test their effects on melatonin formation. Trp is also the hypothesized starting material of melatonin in plants, and TAM is the following intermediate produced by the decarboxylation of Trp. Trp feeding did not affect the contents of melatonin. In contrast, TAM feeding clearly increased the level of melatonin in Viola leaves. Because TAM is derived from Trp, we concluded that the Trp-TAM pathway exists in Viola plants as well. Ineffectiveness of Trp feeding to the change of melatonin contents supports the hypothesis that the decarboxylation step from Trp to TAM is the rate-limiting step in plant melatonin biosynthesis.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.17 no.10
• /
• pp.412-425
• /
• 2016

Recently, the influence of the residential value of new town apartment houses has been increasing in the housing market; however, there has been little study on the relationship between the housing value and customer loyalty. This study analyzed the influence of the housing value on housing satisfaction and customer loyalty. To this end, this study conducted a survey targeting 519 residents in the second term new town. Accordingly, basic statistics, reliability and hypothesis test were carried out using SPSS 21.0 and ANOVA as an analysis method. The study results are as follows. First, as a result of factor analysis of the housing value, the factor was analyzed as 6 sorts, such as safety, sociality, convenience, economic feasibility, aesthetics, and comfort. Second, safety, comfort, and convenience among the factors in the housing value were found to have a significant influence on the housing satisfaction. This means that the concepts of property and assets reflect the development of new urban city apartments. Third, a new town house purchaser's positive housing value and housing satisfaction were found to increase customer loyalty. This greater satisfaction of the current residential apartment dwellers means that they are more likely to introduce their relatives and neighbors. These results suggest that a positive outlook of a new town householder on the housing value and housing satisfaction will eventually work more on revitalizing the housing market.

• Journal of Distribution Science
• /
• v.12 no.8
• /
• pp.123-132
• /
• 2014

Purpose - Recently, Korean companies have been struggling to perform well in the larger smartphone market in China, which is regarded as a blue ocean area. First, it is very important to accurately understand the Chinese consumers, who have a different consumption culture and value system from the Korean culture and system. This would help to identify priorities for the Chinese market. Further, considering the smartphone industry, where technological change is rapid, Korean companies will need to take prompt measures about market trends in order to establish strong competitiveness. Consequently, this study focused on analyzing the relationship between the variables of consumption value, satisfaction, and loyalty in the Chinese smartphone market. The principal dimensions of consumption value, which smartphones have, was analyzed, and the influence on satisfaction was identified. Moreover, the relationship among the variables of satisfaction, attitudinal loyalty, and behavioral loyalty was empirically analyzed. Research design, data, and methodology - This study examined the relationships between various consumption values (functional value, emotional value, social value, epistemic value, and economic value), along with satisfaction and loyalty. The data were collected through a questionnaire survey that was circulated to 310 customers who were users of smartphones in Chingdao and Yeontae regions in China. The survey was conducted from June 23 to August 4, 2013. A total of 301 responses to the questionnaires were collected and used for the data analysis. Moreover, a path analysis based on Lisrel 8.54 was used for the hypothesis test. Results - The variables of functional value, emotional value, social value, and epistemic value were revealed to have positive effects on satisfaction related to smartphone usage. However, the variables of monetary cost and psychological cost were not found to have negative effects on satisfaction related to smartphone usage. Moreover, satisfaction positively influenced attitudinal loyalty related to smartphone usage, but did not have a significant influence on behavioral loyalty related to smartphone usage. Specifically, satisfaction is essential, but not a sufficient condition for building behavioral loyalty in relation to smartphone usage. In addition, attitudinal loyalty positively influenced behavioral loyalty in relation to smartphone usage. Conclusions - First, this study shows that functional value, emotional value, social value, and epistemic value in relation to smartphone usage are important for marketing in the Chinese smartphone market. Particularly, functional value and emotional value play pre-eminent roles as regards customer loyalty in the use of smartphones. Second, the results of this study reveal that the variables of monetary cost and psychological cost are not important to the Chinese consumers. Specifically, the smartphone price and cognitive effort are not perceived as value barriers. Third, satisfaction did not guarantee behavioral loyalty in relation to smartphone usage, and the strategic approach for improving the repurchase and referral action in relation to smartphones based on solid attitudinal loyalty would be desirable and should be the focus of the marketing activities of Korean smartphone companies.

• Journal of Distribution Science
• /
• v.12 no.8
• /
• pp.17-29
• /
• 2014

Purpose - The use of corporate social activities to implement the concept of corporate social responsibility enhances brand equity and attitude, and strengthens economic competitiveness. In areas such as mobile communications, companies take the responsibility of protecting customers and enhance the quality of the mobile communication service, helping to make an effort to obey the regulations of the public trade order and fair trade agreement, enabling a healthy society through communication with elderly living alone or youths without parents, and enhancing marketing strategies. Research design, data, and methodology - To test the hypothesis, a survey was conducted. The surveyed population includes people who use the big three mobile communication services. The survey was conducted from October 4th to October 14th, 2013. A total of 500 survey questionnaires were circulated and 483 were collected; out of these, 32 were excluded due to missing or incomprehensible information. The data was analyzed with SPSS 18.0 via frequency analysis, trust analysis, search factor analysis, relationship analysis, confirmation factor analysis using AMOS 18.0, and structural equation model analysis. Results - Research on corporate social responsibility has been frequently conducted recently. Companies are perceived as social constituents satisfying the social desires of people in addition to customer needs. Further, companies are returning profits to society to satisfy community needs, because there is greater emphasis on the social responsibilities of companies. Companies' social responsibilities should include marketing strategies and the identification of customer needs. This study shows that social service activities influence brand value, which influences customer attitudes; therefore, social service activities indirectly influence customer attitudes. In order to increase customers' purchasing intention, it is essential to improve brand image via social services and provide a distinctive quality of service. Conclusions - This research has used the purposive selection method in the empirical analysis to identify the effect of social services on brand value and customer attitude. Therefore, this study revealed that businesses, whose ultimate objective is to improve customers' purchasing intention, should promote their brand equity through corporate social responsibility activities and offer a distinct service quality. Limitations in the progress of research were found and future indications to overcome these limitations are suggested as follows. First, survey responders had a limited understanding of social responsibilities; therefore, this concept needs to be explained to people first. Second, the research was done on people who live in Daejeon; thus, it is not representative of the entire country. The research has to be repeated with people in other cities. Third, there is a limitation in the study because the purposive selection method was used on Daejeon customers. In the future, a more precise selection of the population is needed. Fourth, Daejeon has unique geographical and size characteristics. Thus, customers in Seoul and other areas may display different characteristics and research on them may reveal different findings. Therefore, again, this study has to be repeated in other areas.

• 한국노년학
• /
• v.37 no.3
• /
• pp.727-745
• /
• 2017

This study purported to examine the effects of precarious employment and social capital on the changes of self-rated health status among the middle aged and the young-old population in South Korea. The study analyzed 12 year follow-up data generated by the Korean Labor and Income Panel Study(KLIPS 6-17), which included 10532 employed subjects aged 55 to 75. Multi-level growth curve modeling was performed by fixed and random effect models using STATA 13.0 program. Afterwards, Hausman test was performed, which resulted in support of the estimation by fixed effect model. The results showed that a day labor position was significant factor affecting the deteriorated changes of self-rated health status over time. In addition, wage, weekly working hours, and private/relational social capitals were also found to be significant factors affecting the changes of the self-rated health status. The results supported the divergence hypothesis as well as the cumulative advantage theory. Efforts should be made to develop and implement various employment support policies and social service programs to alleviate the health inequality of the employed workers over their middle-aged to young-old period.

• The Journal of the Korea Contents Association
• /
• v.19 no.10
• /
• pp.593-606
• /
• 2019

This study examines effective message strategies that fit with the characteristics of retargeting advertisements, based on the Construal Level Theory. First, we investigate whether the social distance that applies between interpersonal interactions can also be observable in an online environment and test the effects of social distance, depending on the type of online sites. We then examine consumers' construal level when social and temporal distances interplay, and how the effects of the messages change accordingly. As a result, social distance and message construal levels by website type were consistent with existing CLT studies. However, the hypothesis that advertising effects will be higher only when all, multidimensions' distances and construal levels of messages match, was partially supported. Also the current view, that the consumers' evaluations will show no difference to when either or both dimensions are distal, was rejected. Instead, when a discrepancy between temporal and social distance was present, the construal level of the message was more effective when congruent with the social distance out the two dimensions. Hence, it is possible to infer that the influence of psychological distance may vary depending on the dimension of distance.

• Journal of Digital Convergence
• /
• v.17 no.10
• /
• pp.209-221
• /
• 2019

Cooperating with a supplier with professional skills is necessary to achieve performance in the development of the innovative products. It is also important to improve development competence and share knowledge. This study empirically analyzed the effect of participant's Job Competence and Leadership Competence on Knowledge Sharing, and the effect of Purchaser Interdependence on Supplier Absorption Capacity. The purpose of the study is to confirm that Knowledge Sharing between Development Participant and Supplier contributes to Performance and to demonstrate the need for a cooperative relationship with the Supplier. A survey was conducted on the product development participants to confirm the relationship between the factors using a Structural Equation Model. As a result of the hypothesis test, the better the Individual Competence of the development participants, the better the Knowledge Sharing Activity, and then Knowledge Sharing and Interdependence are the main factor in the Absorption Capacity of the Supplier. The results of this study can contribute to improving the Supplier Absorption Capacity in the product development projects in which high technology is converged. In the future, we will study the effects of the project support activities of related departments for Performance.