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A Study on Tests for Zero-Inflated Poisson Regression
정광모 한국자료분석학회 2019 Journal of the Korean Data Analysis Society Vol.21 No.6
In analyzing counts data we sometimes encounter excessive zeros than that can be expected under Poisson distributional assumption. For this kind of data we are to model by an alternative counts distribution such as the zero-inflated Poisson distribution. There have been many tests for zero-inflated distribution against the Poisson distribution; the score test, the likelihood ratio test, and the Vuong test. Each of these tests has some limitation in applying under the nonstandard conditions of boundary constraints and non-nested relationships between models. Some researches suggested the weighted sum of independent chi-squared random variables as an asymptotic distribution of the likelihood ratio test but it is not fully studied in the case of non-nested models, in which the Vuong test can generally be used to compare two competing models. We are purposed to recommend an appropriate testing procedure that performs well in both of level controls and higher powers when we are to compare the ordinary Poisson versus zero-inflated Poisson models. We conduct an empirical study to compare the tests for zero-inflated Poisson regression in respect of powers and level controls based on the different asymptotic distributions.
A Study on Criteria for Determining the Number of Clusters
정광모,성주현 한국자료분석학회 2006 Journal of the Korean Data Analysis Society Vol.8 No.4
Determining the number of clusters is a very important issue in cluster analysis. Even though there are many criteria for the number of clusters we have no fully general and satisfactory one for every clustering method. Three main criteria used in commercial statistical packages are discussed through a small Monte Carlo study in the respect of detecting the correct number of clusters in hierarchical clustering.
Dispersion Parameter of Poisson-Gamma Model in the Small Area Estimation
정광모,양혜령 한국자료분석학회 2009 Journal of the Korean Data Analysis Society Vol.11 No.1
The Poisson-gamma model is useful as a population model for estimating the means of small areas. We consider the Empirical Bayes estimator and the confidence interval for small area mean. When sample sizes are small we frequently encounter the inaccuracy in estimating the dispersion parameters provided the inverse dispersion parameter is small. We investigate the statistical properties of mean squared error and the confidence interval in terms of coverage probability through a Monte Carlo simulation study. In this paper we are restricted to the gamma prior with fixed parameters but it would be more reasonable to assume hierachical prior distributions for the parameters. Furthermore we may consider a Poisson loglinear model for the Poisson mean if auxiliary information of covariates is available. The Poisson-gamma model is useful as a population model for estimating the means of small areas. We consider the Empirical Bayes estimator and the confidence interval for small area mean. When sample sizes are small we frequently encounter the inaccuracy in estimating the dispersion parameters provided the inverse dispersion parameter is small. We investigate the statistical properties of mean squared error and the confidence interval in terms of coverage probability through a Monte Carlo simulation study. In this paper we are restricted to the gamma prior with fixed parameters but it would be more reasonable to assume hierachical prior distributions for the parameters. Furthermore we may consider a Poisson loglinear model for the Poisson mean if auxiliary information of covariates is available.
정광모 대한에이즈예방협회 1995 레드리본 Vol.5 No.-
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정광모,방명석 대한안전경영과학회 2011 대한안전경영과학회 학술대회논문집 Vol.2011 No.11
본 논문에서는 지하공간에 설치되는 지중구조물에 대한 내진해석에 관한 연구로 구조물의 거동특성과 내진설계방법의 종류에 따라 수치해석을 실시하였다. 이를 위해 현재 가장 많이 실무에 적용되고 있는 내진설계방법인 등가정적해석법과 응답변위법을 적용하고 정밀한 해석이 가능한 시간이력해석법에 의해 검증을 시행하였으며 구조물 내진해석은 3-D 모델링에 의해 구조물-지반 상호작용을 고려하고 국내의 콘크리트구 조설계기준에 따라 수행하였다. 해석 결과 현재 실무에서 적용되고 있는 등가정적해석법과 응답변위법을 적용하는 경우 정밀한 동적해석법 보다 다소 크게 산정되어 실무 적용에 문제가 없음을 확인 할 수 있었다. In this paper various numerical analyses are carried out according to behavior characteristics of structures and types of seismic design methods as a study on the seismic analysis for underground structures. Equivalent Static Force Procedure and Response Displacement Method commonly used in practiral design are adopted and Time History Method regarded as the most accurate analysis method is selected to verify the results of two practical methods above. 3-D modelling for seismic analysis of structures is introduced to consider Structure Soil Interaction and all analyses are based on Korea Structural Concrete Design Code. After numerical analyses, Equivalent Static Force Procedure and Response Displacement Method showed relatively lager values than those of Time History Method, so it is identified that above two methods are suitable for practical design purpose.