• Communications for Statistical Applications and Methods
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• v.13 no.2
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• pp.429-440
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• 2006

In statistical computing, it is often for researchers to need the distribution of a weighted sum of noncentral chi-square variables. In this case, it is very limited to know its exact distribution. There are many works to contribute to this topic, e.g. Imhof (1961) and Solomon-Stephens (1977). Imhof's method gives good approximation to the true distribution, but it is not easy to apply even though we consider the development of computer technology Solomon-Stephens's three moment chi-square approximation is relatively easy and accurate to apply. However, they skipped many details, and their simulation is limited to a weighed sum of central chi-square random variables. This paper gives details on Solomon-Stephens's method. We also extend their simulation to the weighted sum of non-central chi-square distribution. We evaluated approximated powers for homogeneous test and compared them with the true powers. Solomon-Stephens's method shows very good approximation for the case.

• Journal of the Korean Data and Information Science Society
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• v.18 no.3
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• pp.697-704
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• 2007

It is common in financial time series that volatility(conditional variance) as a measure of risk exhibits asymmetry in such a manner that positive and negative values of return rates of the series tend to provide different contributions to the volatility. We are concerned with asymmetric conditional variances for Korean financial time series especially during the time span of 2000-2001. Notice that these periods suffer from 9-11 disaster in US and collapses of stock prices of dot-companies in Korea. Threshold-ARCH models are considered and a Wald test of asymmetry is suggested. News impact curves are illustrated for graphical representations of leverage effects inherent in various Korean financial time series.

• Journal of Integrative Natural Science
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• v.5 no.4
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• pp.241-245
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• 2012

Categorical data collected based on complex sample design is not proper for the standard Pearson multinomial-based chi-squared test because the observations are not independent and identically distributed. This study investigates effects of bias of point estimator of population proportion and its variance estimator to the standard Pearson chi-squared test statistics when the sample is collected based on complex sampling scheme. This study examines the effect under two population homogeneity test. The standard Pearson test statistic can be partitioned into two parts; the first part is the weighted sum of ${\chi}^2_1$ with eigenvalues of design matrix as their weights, and the additional second part which is added due to the biases of the point estimator and its variance estimator. Our empirical analysis shows that even though the bias of point estimator is small, Pearson test statistic is very much inflated due to underestimate the variance of point estimator. In the connection of design-based variance estimator and its design matrix, the bigger the average of eigenvalues of design matrix is, the larger relative size of which the first component part to Pearson test statistic is taking.

• The Journal of Asian Finance, Economics and Business
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• v.8 no.3
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• pp.139-154
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• 2021

This study's impetus is to explore fresh evidence to answer the question, i.e., whether remittances asymmetrically influence financial development in Bangladesh from 1975 to 2019. The study employs several tests, i.e., nonlinear unit root test, Autoregressive Distributed Lagged (ARDL), NARDL, and asymmetric causality test for establishing the pattern of association. Nonlinear unit root tests confirm that variables follow a nonlinear system of being stationary after the first difference. nonlinearity among variables is investigated by performing the BDS test and nonlinear OLS. Directional causality is investigated through both linear and nonlinear effects of remittance inflows by following the non-granger casualty test. The test statistics of Fpass and tBDM showed the Long-run cointegration in the empirical model and positive effect running from remittances inflow to financial development both in the long-run and short-run. Furthermore, the results of a standard Wald test divulge the presence of long-run and short-run asymmetry. Asymmetry causality test established unidirectional causality due to positive and negative shocks in remittances inflows to Bank-based financial development and feedback hypothesis hold for explaining causality between positive and negative shocks in remittance inflows and Stock-based financial development.

• The Journal of the Korean dental association
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• v.54 no.11
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• pp.840-849
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• 2016

The purpose of this study was to examine dental care utilization and expenditures among children aged 0 to 19 years using Korea Health Panel Survey (KHPS) data in 2008 - 2013. Weighted estimates were nationally representative and statistical significances were analysed by $x^2$ test or adjusted Wald test using STATA 13 software. While dental care utilization increased steadily among children from 2008 through 2013, less than one-third the children received dental care in 2013. Compared with 2008, the proportion of restorative care, oral surgery, preventive care decreased and the proportion of orthodontic care, prosthetic care increased. While the proportion of amalgam markedly decreased, the proportion of resin increased. This study highlight socioeconomic disparities in dental utilization and expenditures among children. Especially the findings provide a baseline assessment for examining trends on dental care for children in the future.

• The Journal of Asian Finance, Economics and Business
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• v.7 no.11
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• pp.877-883
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• 2020

The purpose of the article is to evaluate the factors that affect the degree of environmental accounting information disclosure. Data are collected from 87 industry companies listed on the Vietnamese stock market from 2009 to 2019. I focus on the effect of factors such as the Firm size, Profitability, Leverage, Firm age, and Independent auditors. To explain the causal relationship between factors, I construct the regression model and then test it by using different statistical method approaches, including the pooled OLS, the fixed effects model, and the random effects model. Then I conduct testing of model defects: White Test, Wooldridge Test, Hausman Test, and Wald Test. The Feasible Generalized Least Squares (FGLS) method is used to analyze the image factors that affect environmental accounting information disclosure. The results show that the extent of environmental accounting information disclosure is influenced by factors: firm size, uptime and independent audit. These factors positively affect the level of environmental accounting information disclosure; independent audit has the greatest influence. Based on the research results, the author gives recommendations to improve the disclosure of environmental accounting information for industrial enterprises listed on the Vietnamese stock market, increasing the competitiveness of the public company in terms of global integration.

• Journal of Korea Technology Innovation Society
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• v.17 no.3
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• pp.449-466
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• 2014

There have been various researches on the relationship between a company's R&D investment and the outcome from innovation. However, these studies failed to effectively analyze the decision-making process followed by companies in relation to knowledge production. Especially, in analyzing the patent of companies, the Poisson model has been commonly used, but its limitations have been pointed out. In recent years, many studies have adopted negative binomial models, but they still pose limitations in analyzing the selection process. This paper proposed a hurdle negative binomial model to effectively reflect the company's decision embedded within patent information and conduct an empirical analysis on a survey of businesses' activities. In particular, the study analyzed the selection process of companies in determining the number of patents. As a result of estimation, the presence of over-dispersion was identified. In addition, the Wald-test confirmed that setting up of hurdles was valid, and there was a difference between the results of hurdle models and those of general negative binomial settings.

• Proceedings of the Korean Society of Agricultural Engineers Conference
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• 2005.10a
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• pp.284-287
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• 2005

The objective of this study is to check into variation trends of design rainfall according to change of the number of years for observed data. To make comparative study of the relation between design rainfall and recorded year, this study was used maximum rainfall for 24-hr consecutive duration at Gangneung, Seoul, Incheon, Chupungnyeong, Pohang, Daegu, Jeonju, Ulsan, Gwangju, Busan, Mokpo and Yeosu rainfall stations. The tests for Independence, Homogeneity and detection of outliers were used Wald-Wolfowitz's test, Mann-Whitney's test and Grubbs and Beck test respectively. To select appopriate distribution, the distribution of genaralized pareto(GPA), generalized extreme value(GEV), generalized logistic(GLO), lognormal and pearson type 3 distribution is judged by L-moment ratio diagram and Kolmogorov-Smirnov (K-S) test. Design rainfall was estimated by at-site frequency analysis using L-moments and Generalized extreme value(GEV) distribution according to change of the number of years for observed data. Through the comparative analysis for design rainfall induced by L-moments and GEV distribution, relationship between design rainfall and recorded year is provided.

• Journal of The Korean Society of Agricultural Engineers
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• v.51 no.4
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• pp.49-55
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• 2009

This paper is to induce design floods through L-moment with 3 and 4 parameter Kappa distributions including test of independence by Wald-Wolfowitz, homogeneity by Mann-Whitney and outlier by Grubbs-Beck on annual maximum flood flows at 9 water level gaging stations in Han, Nakdong and Geum Rivers of South Korea. After analyzing appropriateness of the data of annual maximum flood flows by Kolmogorov-Smirnov test, 3 and 4 Kappa distributions were applied and the appropriateness was judged. The parameters of 3 and 4 Kappa distributions were estimated by L-moment method and the design floods by water level gaging station was calculated. Through the comparative analysis using the relative root mean square errors (RRMSE) and relative absolute errors (RAE) calculated by 3 and 4 parameter Kappa distributions with 4 plotting position formulas, the result showed that the design floods by 4 parameter Kappa distribution with Weibull and Cunnane plotting position formulas are closer to the observed data than those obtained by 3 parameter Kappa distribution with 4 plotting position formulas and 4 parameter Kappa distribution with Hazen and Gringorten plotting position formulas.

• The Journal of Asian Finance, Economics and Business
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• v.8 no.1
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• pp.23-36
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• 2021

The study explores the nexus between foreign direct investment (FDI), financial innovation, and exchange rate volatility in selected South Asian countries for 1980 to 2017. The study applies the unit root test, Autoregressive Distributed Lagged, nonlinear ARDL, and causality test following Toda-Yamamoto. Unit root tests ascertain that variables are integrated in a mixed order; few variables are stationary at a level and few after the first difference. Empirical model estimation with ARDL, Long-run cointegration revealed with the tests of FPSS, WPSS, and tBDM by rejecting the null hypothesis of "no cointegration." This finding suggests that, in the long-run financial innovation, FDI inflows, and exchange rate volatility move together. Moreover, study findings established adverse effects running from FDI inflows and financial innovation to exchange rate volatility in the long run. These findings suggest that continual FDI inflows and innovativeness in the financial system assist in lessening the volatility in the foreign exchange market. Furthermore, nonlinear ARDL confirms the presence of asymmetric cointegration in the model. The standard Wald test established asymmetric effects running from FDI inflows and financial innovation to exchange rate volatility, both in the long and short run. Directional causality unveils feedback hypothesis holds for explaining causality between FDI, financial innovation, and exchange rate volatility.