• Communications for Statistical Applications and Methods
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• 제26권1호
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• pp.11-25
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• 2019

The present paper utilizes auxiliary information to neutralize the effect of non-response for estimating the population mean. Improved ratio type estimators for population mean have been proposed and their properties are studied. These estimators are suggested for both single phase sampling and two phase sampling in presence of non-response. Empirical studies are conducted to validate the theoretical results and demonstrate the performance of the proposed estimators. The proposed estimators are shown to perform better than those used by Cochran (Sampling Techniques (3rd ed), John Wiley & Sons, 1977), Khare and Srivastava (In Proceedings-National Academy Science, India, Section A, 65, 195-203, 1995), Rao (Randomization Approach in Incomplete Data in Sample Surveys, Academic Press, 1983; Survey Methodology 12, 217-230, 1986), and Singh and Kumar (Australian & New Zealand Journal of Statistics, 50, 395-408, 2008; Statistical Papers, 51, 559-582, 2010) under the derived optimality condition. Suitable recommendations are put forward for survey practitioners.

• 대한공간정보학회지
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• 제18권1호
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• pp.129-134
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• 2010

저탄소 녹색성장은 국내외적으로 중요한 정치적 이슈가 되고 있으며, 한국정부는 최근 저탄소 녹색성장을 위한 비젼을 발표하였다. 이런 관점에서 탄소배출 추정은 도시계획에 있어서 중요한 요소가 되고 있다. 탄소저감 계획을 수립하기 위하여 본 연구에서는 과거 40년 동안 진주시의 탄소배출 추정과 토지이용변화의 상호추이변화를 분석하였다. 토지적성평가 데이터베이스와 항공영상의 영상처리자료는 과거 40년간의 토지이용변화를 분석하는데 유효한 정보를 주었으며, 신주거지 개발에 의한 토지이용변화는 급격한 인구집중과 탄소배출증가를 가져왔다. 앞으로 저탄소 녹색성장을 위한 도시관리계획에 있어서 토지이용변화에 따른 탄소배출 증가를 계획수립 시 반드시 고려해야하며, 향 후 토지이용과 연료소비추정이 포함된 정확한 탄소배출 추정모델개발에 대한 추가적인 연구가 필요하다고 사료된다.

• 대한교통학회지
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• 제12권1호
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• pp.85-95
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• 1994

While bicycles are an exhaust-free and low energy consuming mode of transport, the use of them is getting decreased. The aim of this research is to find out current levels of bicycle ownership and to estimate the ownerships of the bicycles by spatial structure and social factors in the metropolitan area. The parameters which affect on the characteristics of the bicycle ownership are classified into aggregate and disaggregate categories. The ownerships of the bicycles are estimated by the multiple regression analysis using urban characteristics data and the binary logit analysis using household characteristics data. The results of this study to population, car ownership, and number of male in the household, and negatively by the population density.

• Journal of the Korean Data and Information Science Society
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• 제15권4호
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• pp.973-980
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• 2004

Phase I clinical trials are often pharmacologically oriented and usually attempt to find the best dose of drug to employ. However, other purposes like determination of sizes and types of side effects and toxicity and organ system involved are equally important. Estimation of treatment effects or side effects is usually ignored since it is usually based on too small sample, even though Phase II clinical trials would be designed based on the Phase I studies. Statistical methods for constructing the approximate confidence interval for population median in case of small sample are considered and an improved method is proposed. The proposed estimator is compared with current methods through simulation studies.

• Communications for Statistical Applications and Methods
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• 제21권2호
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• pp.169-181
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• 2014

Marginalized random effects models (MREM) are commonly used to analyze longitudinal categorical data when the population-averaged effects is of interest. In these models, random effects are used to explain both subject and time variations. The estimation of the random effects covariance matrix is not simple in MREM because of the high dimension and the positive definiteness. A relatively simple structure for the correlation is assumed such as a homogeneous AR(1) structure; however, it is too strong of an assumption. In consequence, the estimates of the fixed effects can be biased. To avoid this problem, we introduce one approach to explain a heterogenous random effects covariance matrix using a modified Cholesky decomposition. The approach results in parameters that can be easily modeled without concern that the resulting estimator will not be positive definite. The interpretation of the parameters is sensible. We analyze metabolic syndrome data from a Korean Genomic Epidemiology Study using this method.

• Fisheries and Aquatic Sciences
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• 제27권4호
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• pp.207-212
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• 2024

The study was conducted at Lake Hayq, one of the lakes of Wollo, Ethiopia. Data were collected at the landing sites for 365 days (June 8, 2022 to June 7, 2023). The basic information gathered in the fishing part of the Lake was Nile tilapia caught by fishermen, the total number of tilapia and the increase in fishing effort. The aim of the research was to estimate the size of the Nile tilapia population and the fishing mortality rate in length groups for Nile tilapia stocks occurring in the lake. A Jones length-based cohort analysis model was used to estimate Nile tilapia population. The estimated Nile tilapia population was over 46.8 Million tilapia per year. The model estimates that more than 13.3 million 8-10 cm Nile tilapia are caught in fisheries each year.

• Communications for Statistical Applications and Methods
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• 제20권6호
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• pp.439-454
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• 2013

This study presents a Bayesian multiple change-point detection approach to segment and classify the observations that no longer come from an initial population after a certain time. Inferences are based on the multiple change-points in a sequence of random variables where the probability distribution changes. Bayesian multiple change-point estimation is classifies each observation into a segment. We use a truncated Poisson distribution for the number of change-points and conjugate prior for the exponential family distributions. The Bayesian method can lead the unsupervised classification of discrete, continuous variables and multivariate vectors based on latent class models; therefore, the solution for change-points corresponds to the stochastic partitions of observed data. We demonstrate segmentation with real data.

• Journal of the Korean Data and Information Science Society
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• 제26권2호
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• pp.377-385
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• 2015

표본조사에서 무응답이 발생한 개체에 대해 재조사 실시한 후 보조변수를 사용한 회귀추정의 형태를 가지는 추정량을 제시하고 복제치 기법을 이용한 분산추정량을 연구한다. 또한 응답여부에 따른 응답확률의 모수적 추론방법도 함께 제시한다. 재조사 후 모평균에 대하여 불편성을 만족하고 효율이 좋은 추정량과 일치성을 가지는 분산추정량을 이론적으로 연구하고 모의실험을 통하여 연구의 타당성을 입증한다.

• Asian Pacific Journal of Cancer Prevention
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• 제13권8호
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• pp.3893-3898
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• 2012

In previous studies we predicted future trends in cancer incidence for each prefecture in order to plan cancer control. Those predictions, however, did not take into account the characteristics of each prefecture. We therefore used the results of age-period-cohort analysis of incidence and mortality data of Osaka, and estimated the incidence and mortality of cancers at all sites and selected sites. The results reflect the characteristics of Osaka, which has and is expected to have large number of patients with liver cancer. We believe our results to be useful for planning and evaluating cancer control activities in Osaka. It would be worthwhile to base the estimation of cancer incidence and mortality in each prefecture on each population-based cancer registry.

• 산업경영시스템학회지
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• 제22권52호
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• pp.1-8
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• 1999

This study was conducted to collect data concerning the preferred driving postures and adopted seat adjustment levels and to grasp relationships among drivers' body sizes, postural angles, and adopted seat positions and angles. Also optimum driving posture and seat adjustment level estimation models were constructed. An experiment was conducted to investigate observed optimum driving posture, and seat adjustment level. Thirty-six subjects (male=20, female=16) was selected to include a wide range of percentiles in the dimensions important for automotive driving workstation design and to be representative of the automotive driving population in Korea. New guidelines and estimation models for optimum postural comfort were developed. There were significant differences between male and female in postural angles but not in seat adjustment levels. Taller subjects preferred a more open and reclined posture. Estimation models enable us to estimate the quantitative optimum driving posture and seat adjustment level with some drivers' physical dimensions.