• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.5
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• pp.2251-2258
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• 2012

This study compared the unweighted sample design, frequency weighted sample design and complex sample design to using 2009 Korea National Health and Nutrition Examination Survey in an effort to identify whether or not there is any difference in potential risk factors. Pearson chi-square test and Rao-scott chi-square test were applied to the analytic methods. As a result of analyses, all the variables were overestimated as significant risk factors in case of the unweighted sample design to which only the frequency weights were applied. In addition, there were differences in the confidence levels and results from the simple random sampling analysis and complex sample design to which no weight was applied. It is necessary to carry out the complex sample design rather than the analysis to which the frequency weights are applied, in order to ensure the findings to represent the whole population when our national statistics data is used.

• Survey Research
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• v.7 no.2
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• pp.53-69
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• 2006

Weights can be made and imposed in both sample design stage and analysis stage in a sample survey. While in design stage weights are related with sample data acquisition quantities such as sample selection probability and response rate, in analysis stage weights are connected with external quantities, for instance population quantities and some auxiliary information. The final weight is the product of all weights in both stage. In the present paper, we focus on the weight in analysis stage and investigate the effect of such weights imposed on the weighted mean when estimating the population mean. We consider a finite population with a pair of fixed survey value and weight in each unit, and suppose equal selection probability designs. Under the condition we derive the formulas of the bias as well as mean square error of the weighted mean and show that the weighted mean is biased and the direction and amount of the bias can be explained by the correlation between survey variate and weight: if the correlation coefficient is positive, then the weighted mein over-estimates the population mean, on the other hand, if negative, then under-estimates. Also the magnitude of bias is getting larger when the correlation coefficient is getting greater. In addition to theoretical derivation about the weighted mean, we conduct a simulation study to show quantities of the bias and mean square errors numerically. In the simulation, nine weights having correlation coefficient with survey variate from -0.2 to 0.6 are generated and four sample sizes from 100 to 400 are considered and then biases and mean square errors are calculated in each case. As a result, in the case or 400 sample size and 0.55 correlation coefficient, the amount or squared bias of the weighted mean occupies up to 82% among mean square error, which says the weighted mean might be biased very seriously in some cases.

• The Korean Journal of Applied Statistics
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• v.10 no.2
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• pp.215-226
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• 1997

The purpose of the labor statistics survey is to collect materials on employment, wages and the working time and to analyze the trend of the labor situation. in this research, the stratification variables are industry and the size of establishment. The sample are selected by stratified one stage sampling method in order to produce the reliable estimates of labor statistics. For local labor statistics, we design the sample survey using the city and province as sub-population. So we are able to produce the local area estimates of labor statistics with respect to industry and the size of establishment.

• Journal of the Korean Society of Food Culture
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• v.19 no.4
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• pp.460-467
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• 2004

Survey on the usage of commercial poggi Kimchi was run and consumer's acceptance test of the Kimchi in the various regions of Korea including Seoul(SE), Kyonggi Province(KG), Kangwon Province(KW), Kyungsang Province(KS), and Jeonla Province(JL) were investigated. Survey result of 34% of consumer showed that they eat Kimchi very much, and 19% answered they ate Wimchi whenever they had chance to eat. The most desired points of improvement in commercial poggi Kimchi were as following; Taste and degree of fermentation should be standardized. Order of preferences of minor ingredients of Kimchi were radish, hot pepper, welsh onion, and leek, respectively. Consumer acceptance test of KS sample group showed higher preference in whole color, salted condition, spicy hot flavor and crispness than the others. In whole color and pickled seafood properties, KG sample group showed significantly higher values than the others. In salty flavor, SE sample group showed lower preference than the others.

• Survey Research
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• v.3 no.1
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• pp.25-51
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• 2002

We examine the response patterns to web survey with a series of experiments embedded in a survey of students at the Sookmyung Women's University. A sample of 960 students was sent e-mail invitation to participate in a internet survey, The response rate was 53.9% except partial and overall non-response. Methodological experiments included the use of a pre-notification, reminder notices as well as the type of questionnaire. These factors that manipulate the perceived burden of the task had an effect on the likelihood of accepting the survey invitation. This paper discusses the overall implementation and outcome of the survey, and describes the results of the imbedded design experiments. Also we compared the representative of self-selected and probability sample.

• Journal of Environmental Impact Assessment
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• v.30 no.3
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• pp.155-163
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• 2021

The number of trees to be removed trees (ART) in the environmental impact assessment is an environmental indicator used in various parts such as greenhouse gas emissions and waste of forest trees calculation. Until now, the ART has depended on the forest tree density of the vegetation survey, and the uncertainty of estimating the amount of removed trees has increased due to the sampling bias. A full-scale survey can be offered as an alternative to improve the accuracy of ART, but the reality is that it is impossible. As an alternative, there is an individual tree detection using aerial image (ITD), and in this study, we compared the ARTs estimated by full-scale survey, sample survey, and ITD. According to the research results, compared to the result of full-scale survey, the result of ITD was overestimated by 25. While 58 were overestimated by the sample survey (average). However, as the sample survey is an estimate based on random samples, ART will be overestimated or underestimated depending on the number and size of quadrats.

• The Korean Journal of Applied Statistics
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• v.3 no.1
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• pp.27-46
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• 1990

In this paper, wer propose many problems by analyzing the various currently statistics, propose the basic principal for the more precise performance of sample survey, and at the same time propose the method(principal) for detecting and manipulationg the source of error. Finally, we are to improving the statistical reliability and increasing the user's convenience by standardizing the statistical reporting form.

• Journal of the Korean Data and Information Science Society
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• v.13 no.1
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• pp.35-45
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• 2002

For improving the quality of survey dat a of sensitive character, we suggest a conditional in direct survey method. In th at method, only the respondents who answer directly to the less sensitive question respond indirectly to the more sensitive one by using the one sample unrelated question randomized response technique with the known $\pi_y$, the true proportion of unrelated group Y. We extend it to two sample method when $\pi_y$ is unknown. We also consider the case that people who possess less sensitive character answer untruthfully. Finally we compare our method with the methods of Greenberg et al. and Carr et al..

• Communications for Statistical Applications and Methods
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• v.10 no.2
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• pp.553-566
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• 2003

In many cases, the measurement error variances may be functions of the unknown true values or related covariates. This paper considers design-based estimators of the parameters of these variance functions based on the within-unit sample variances. This paper devotes to: (1) define an error scale factor $\delta$; (2) develop estimators of the parameters of the linear measurement error variance function of the true values under large-sample and small-error conditions; (3) use propensity methods to adjust survey weights to account for possible selection effects at the replicate level. The proposed methods are applied to medical examination data from the U.S. Third National Health and Nutrition Examination Survey (NHANES III).

• Communications for Statistical Applications and Methods
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• v.16 no.2
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• pp.317-323
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• 2009

Recently not even government polices but small town decisions are based on the survey data/information, so the most of government agencies/organizations demand various sample surveys in each fields for more detail information. However in conducting the sample survey, nonresponse problem rises very often and it becomes a major issue on judging the accuracy of survey. For that matters, one solution ran be using the administration data. However unfortunately most of administration data are restricted to the common users. The other solution can be the imputation. Therefore several method, of imputation are studied in various fields. In this study, in stead of the simple regression imputation method which is commonly used, factor score regression method is applied specially to the incomplete data which have the unit and item misting values in survey data. Here for simulation study, Consumer Expenditure Surveys in Korea are used.