• Communications for Statistical Applications and Methods
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• v.10 no.2
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• pp.507-517
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• 2003

Self-organizing map (SOM) has been developed mainly by T. Kohonen and his colleagues as a unsupervised learning neural network. Because of its topological ordering property, SOM is known to be very useful in pattern recognition and text information retrieval areas. Recently, data miners use Kohonen´s mapping method frequently in exploratory analyses of large data sets. One problem facing SOM builder is that there exists no sensible criterion for evaluating goodness-of-fit of the map at hand. In this short communication, we propose valid evaluation procedures for the Kohonen SOM of any size. The methods can be used in selecting the best map among several candidates.

• Journal of the Korean Statistical Society
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• v.26 no.2
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• pp.199-210
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• 1997

Using regression methods based on quasi-likelihood equation, one only needs to specify the conditional mean and variance functions for the response variable in the analysis. In this paper, an omnibus lack-of-fit test is proposed to test the validity of these two functions. Our test is consistent against the alternative under which either the mean or the variance is not the one specified in the null hypothesis. The large-sample null distribution of our test statistics can be approximated through simulations. Extensive numerical studies are performed to demonstrate that the new test preserves the prescribed type I error probability. Power comparisons are conducted to show the advantage of the new proposal.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.24 no.9 s.180
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• pp.2353-2360
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• 2000

Statistical fatigue properties of metallic materials are increasingly required for reliability design purpose. In this study, static and fatigue tests were conducted and the normal, log-normal, two -parameter Weibull distributions at the 5% significance level are compared using the Kolmogorov-Smirnov goodness-of-fit test. Parameter estimation were compared with experimental results using the maximum likelihood method and least square method. It is found that two-parameter Weibull distribution and maximum likelihood method provide a good fit for static and fatigue life data. Therefore, it is applicable to the static and fatigue life analysis of the spheroidal graphite cast iron. The P-S-N curves were evaluated using log-normal distribution, which showed fatigue life behavior very well.

• Korean Management Science Review
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• v.19 no.2
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• pp.59-73
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• 2002

There have been academic debates upon which measure is more desirable in measuring service quality between SERVQUAL and SERVPERF In addition, Korean fast food industry is rapidly growing due to increasing income and globalization. Our study tried to contribute to both academic and practical issues. We compared SERVQUAL and SERVPERF measures to determine which one is superior to measure service quality in Korean fast food franchise. We collected data from two branch restaurants of one American global fast food franchise system. Regression analyses resulted in that SERVPERF outperformed SERVQUAL. Furthermore, we compared the goodness of fit of the two structural equation models of SERVQUAL anO SERVPERF, respectively. The SERVPERF model showed a much better model fit than the SERVQUAL model did. Thus, we suggest that SERVPERF be used to measure service quality in Korean fast food industry.

• The Korean Journal of Applied Statistics
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• v.2 no.2
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• pp.79-89
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• 1989

Modified Pearson $X^2$ statistic is concerned. Moreover the four statistics(Pearson, Wald, modified sample design effects and reduction factor) are compared in one-stage sampling situation. In case of categorical of fit and independence tests for sample data above, it is shown that there is a significant behavior between Pearson $X^2$ and Wald statistic, but minor difference in modified statistics by simulation methods.

• Wind and Structures
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• v.21 no.2
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• pp.203-221
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• 2015

Wind speed is the most important parameter in the design and study of wind energy conversion systems. The weibull distribution is commonly used for wind energy analysis as it can represent the wind variations with an acceptable level of accuracy. In this study, the wind data for 11 cities in Iran have been analysed over a period of one year. The Goodness of fit test is used for testing data fit to weibull distribution. The results show that this data fit to weibull function very well. The scale and shape factors are two parameters of the weibull distribution that depend on the area under study. The kinds of numerical methods commonly used for estimating weibull parameters are reviewed. Their performance for the cities under study was compared according to root mean square and wind energy errors. The result of the study reveals the empirical, modified maximum likelihood estimate of wind speed with minimum error. Also, that the moment and modified maximum likelihood are the best methods for estimating the energy production of wind turbines.

• Journal of Fisheries and Marine Sciences Education
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• v.29 no.2
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• pp.466-478
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• 2017

The purpose of this study was to examine the relationships between perceived parental attachment and the life satisfaction of college students, focusing on the mediating role of psychological basic needs(autonomy, competence and relatedness). The Participants of this study were 208 college students. The result was statistically treated using SPSS 21.0 program, Amos 21.0. Additionally, PROCESS Macro was used to verify the significant mediating effect. Results from structural equation modeling analyses indicated that a research model produced a better fit to the data than a alternative structural model. The final SEM model fit indices of $x^2$(df), CFI, TLI, RMSEA were met the acceptable criteria of model fitness. In other words, among the goodness-of-fit indexes of the final study model, $x^2=261.075$(p<.001), RMSEA is .082, TLI equals .925, CFI equals .940. The results showed the following: First, Parental attachment has a direct effect on autonomy, competence and relatedness. Also competence and relatedness have a direct effect on the life satisfaction. Second, Competence and relatedness showed a mediating effects on Parental attachment and the life satisfaction. The implications of these results were discussed and the further studies were suggested.

• Transactions of Materials Processing
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• v.32 no.6
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• pp.352-359
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• 2023

Recently, independent suspension systems have been applied not only to passenger cars but also to large commercial vehicles. Therefore, the need for research to domestically produce such independent suspensions for large commercial vehicles is gradually increasing. In this paper, we conducted research on the manufacturing technology of the relay lever, which are integral components of independent suspension systems for large commercial vehicles. Our goal was to reduce the flash volume generated during the forging process. The shape variables of the initial billet were adjusted to find proper forming conditions that could minimize flash volume while performing product forming smoothly. Shape variables were set as input variables and the flash volume was set as an output variable, and simulations were carried out to analytically predict the volume of the flash area for each variable condition. Based on the data obtained through numerical simulations, a regression model and an artificial neural network model were used to develop a prediction model that can easily predict the flash volume for variable conditions. For the corresponding prediction model, a goodness of-fit test was performed to confirm a high level of fit. By comparing and analyzing the two prediction models, the high level of fit of the ANN model was confirmed.

• Human Ecology Research
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• v.58 no.2
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• pp.149-161
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• 2020

This study showed that the association between grandmother-mother relationship and grandmother-grandchildren ties is mediated by the coparenting. Participants consisted of 329 grandmothers who were rearing preschool aged grandchildren in the Seoul and Gyeonggido area. SPSS 23.0 performed descriptive statistical analysis and correlation analysis. The structural equation model was estimated with AMOS 23.0. Parameters were estimated using the maximum likelihood method. Model fit index used the chi-square statistic, the goodness of fit index (GFI), the Turker-Lewis index (TLI), the comparative fit index (CFI), the root mean square error of approximation (RMSEA). The mediation effect analysis followed a two-step verification process; direct and indirect effect. In addition, statistical significance of the indirect effect was examined using a bootstrapping procedure. The results are as follows. First, a positive correlation was found between the grandmother-mother relationship, grandmother-grandchildren ties, and coparenting. Second, the association between grandmother-mother relationship and grandmother-grandchildren ties is mediated by coparenting. The results of this study suggest that the quality of the grandmother's relationship with mothers and cooperative coparenting is important to building relationships with grandchildren. In addition, coparenting can be an important mechanism for grandmother-mother relationships and grandmother-grandchild ties. Based on the results of this study, we discussed ways to improve the grandmothers' relationship quality with the mother and strengthen parenting ability.

• Journal of Korean Academy of Nursing Administration
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• v.11 no.4
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• pp.371-384
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• 2005

Purpose: The aim of this study was to analysis path model of the research variables. Methods: The subjects of this study were 647 nurses who were working in the 8 general hospitals located in Seoul and Incheon area. The data were collected by self-reporting questionnaires. The data were analyzed using descriptive statistics and path analysis. Results: In the modified path model, overall fitness indexes were $X^2$= 223.27, goodness of fit index=0.90, root mean square residual=0.039, root mean square error of approximation=0.12, non-normed fit index=0.96, and normed fit index=0.90. From the model, among research variables that influence organizational effectiveness motivator, job satisfaction and organizational identification affected directly work performance. In internal marketing factors, paid-leave, communication and reward affected directly motivator. Motivator and hygiene factors affected directly job satisfaction, organizational commitment and organizational identification. Conclusion: With these findings, paid-leave, communication, reward, motivator, job satisfaction and organizational identification were direct or indirect predictors of the work performance. Therefore nursing managers ought to develop internal marketing strategies and motivation enhancing system for nurses based on this path model in order to improve the nursing organizational effectiveness.