• Survey Research
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• v.6 no.1
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• pp.39-62
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• 2005

In this paper we investigate some concepts frequently called in sample surveys such as 'representative of sample' as well as 'consistency', 'unbiasedness', and 'efficiency' in estimation. The first is strongly related with sampling procedure including coverage rate of survey population, response rate in establishment survey, and recruit rate of final samples. The others, however, are concerned with both sampling design and corresponding estimators simultaneously. Whereas both consistency and unbiasedness are based on the representative sample, efficiency does not depend on the representative sample. The representative of sample can be increased by raising the rate of coverage, response and recruit as well. Consistency may be investigated according to variables of interest and auxiliary variables. The well-known raing-ratio weighting method is a method to increase consistency of auxiliary variables by means of matching population size in each cell. Efficiency is not directly related with the representative of sample, and allocation methods such as proportional and Neyman allocation in stratified sampling and post-stratification are all methods to increase the efficiency of estimation under the condition of satisfying the representative of sample.

• The Korean Journal of Applied Statistics
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• v.28 no.3
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• pp.417-427
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• 2015

Measures in response rate used to measure the representativeness of the sample (the more high response rate) better explain the representativeness of the sample. However, we cannot often explain the representativeness of the sample because there is nonresponse even in the high response rate. Therefore, Schouten et al. (2009) presented a new R-indicator measure that can be described as a representative of the sample. We research the new estimator of the R-indicator in this paper because there are parameters that require estimations. We describe the meanings as representative of the R-indicator; consequently, the bias and efficiency of the proposed estimator for R-indicator are compared to the existing estimator under various simulations. The representativeness of the sample is also explained by applying the proposed estimators in the actual data.

• Composites Research
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• v.37 no.3
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• pp.179-185
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• 2024

This study quantitatively evaluated and investigated the changes in transverse tensile strength of unidirectional fiber-reinforced composites with initial void defects using a Representative Volume Element (RVE) model. After calculating the appropriate sample size based on margin of error and confidence level for initial void defects, a sample group of 5000 RVE models with initial void defects was generated. Dimensional reduction and density-based clustering analysis were conducted on the sample group to assess similarity, confirming and verifying that the sample group was unbiased. The validated sample analysis results were represented using a Weibull distribution, allowing them to be applied to the reliability analysis of composite structures.

• Fashion & Textile Research Journal
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• v.13 no.4
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• pp.590-599
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• 2011

The purpose of this study is to classify body types into different groups based on 3D scanned data, and identify the representative body shapes that most frequently appear in the groups. A high frequency range was defined based on body measurement data, and representative shapes were identified based on body scan data of women aged 18-24. The major findings of this study are as follows. First, the three typical types of height, bust and drop mixes among Korean women aged 18-24 are as follows:) 155-88-N,) 160-82-A, and 165-85-A. Regarding the body type, the A and N types frequently appeared, while the H type was rare. Second, among the subjects of the high-frequency groups, upright bodies were selected as sample models and were used for morphing. An adjustment was made to the morphing results to reflect the body characteristics of the sample models evenly. Third, to verify the morphing results, the body sizes of the sample models and the created models were compared. The result showed that, the sizes were close to the average size of the sample models. Fourth, to verify whether the morphing processes adequately reflected the features of the body shapes, cross-section models of key body parts were made and the degree of representativeness was determined.

• Computers and Concrete
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• v.7 no.5
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• pp.469-482
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• 2010

This paper investigates the concrete permeability through a numerical and statistical approach. Concrete is considered as a random heterogeneous composite of three phases: aggregates, interfacial transition zones (ITZ) and matrix. The paper begins with some classical bound and estimate theories applied to concrete permeability and the influence of ITZ on these bound and estimate values is discussed. Numerical samples for permeability analysis are established through random aggregate structure (RAS) scheme, each numerical sample containing randomly distributed aggregates coated with ITZ and dispersed in a homogeneous matrix. The volumetric fraction of aggregates is fixed and the size distribution of aggregates observes Fuller's curve. Then finite element method is used to solve the steady permeation problem on 2D numerical samples and the overall permeability is deduced from flux-pressure relation. The impact of ITZ on overall permeability is analyzed in terms of ITZ width and contrast ratio between ITZ and matrix permeabilities. Hereafter, 3680 samples are generated for 23 sample sizes and 4 contrast ratios, and statistical analysis is performed on the permeability dispersion in terms of sample size and ITZ characteristics. By sample theory, the size of representative volume element (RVE) for permeability is then quantified considering sample realization number and expected error. Concluding remarks are provided for the impact of ITZ on concrete permeability and its statistical characteristics.

• The Mathematical Education
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• v.50 no.4
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• pp.489-505
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• 2011

This study is an analysis on the focus of textbooks regarding the statistical chapters of "measures of representative(central tendency) and of the spread". Applying the summary-concept criteria of Juhyeon Nam(2007), 4 kinds of aspect of the chapter; (1) definition and its teleological validity of the measures of representative, (2) definition and practical value of the measures of spread (3) distributional form on the measures of representative and of spread (4) location and scale preservation or invariance of the measures of representative and of spread were observed. On the measures of representative, some definitions were insufficient to check the teleological validity of the measure. Most definitions of the measure of spread were based on the practical view points but no preparation for the future statistical inferences were found even by implication. Some books mention about the measures of representative and of spread for distributions, but we could not find any comments on the correspondence between the sample mean and the expectation of a distribution or population mean. However it is stimulant that some books check the validity of corresponding measures with the location and scale preservation or invariant property, that were not found in the previous curriculum.

• Journal of the Korean Society of Costume
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• v.55 no.8 s.99
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• pp.144-153
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• 2005

The purpose of this study is to make a Web Color Data Base for practical design system for domestic fashion industry. The market segmentation was based on the results of the previous studies and the characteristics of fashion consumers. Finally, the 14,121 color samples are collected from the survey of 55 manufacturers of domestic fashion industry and 116 fashion brands of major department stores. These color samples are analyzed by the Munsell's H V/C and CIE L*a*b* value. The representative colors are selected concerning the density in CIE L*a*b* color space and the distance between the color samples. As a result, We suggested 2213 representative colors. Also, this color data was constructed on Web site. The data were sorted by the market, season and color code. In addition, the representative color sample book was made for the prototype of .

• Journal of the Korean Geophysical Society
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• v.2 no.4
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• pp.269-276
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• 1999

As a part of trying to get the resistivity values correctly from laboratory core resistivity measurement, the effect of sample holders in resistivity measurement was analyzed and a better way to determine the representative resistivity value from the time series resistivity data was searched. Modified GS type and modified two-electrode type sample holders were devised and their effects have been compared with those of GS and two-electrode type sample holders. The modified two-electrode type sample holder has benefits both in repetition and simplicity in data acquisition. The analysis of distribution trend of the time series resistivity data obtained with different kind of sample holders and source frequencies shows that the maximum curvature point method gives the best result in determining representative resistivity value.

• Proceedings of the Korean Association for Survey Research Conference
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• 2001.04a
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• pp.153-165
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• 2001

In this paper we point out another advantage of systematic sampling over simple random sampling, which have not yet been spelled out in the literature. After a single sample is drawn by a sampling scheme, it is important to check whether the achieved sample represents the pupulation well or out. Therefore, a sampling scheme which avoids the possibility of selecting non-preferred samples is desirable. The simulation results are given to illustrate that, in the ordered population, the possibility of selecting non-preferred sample by systematic sampling is lower than that by simple random sampling.

• Survey Research
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• v.2 no.2
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• pp.153-165
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• 2001

In this paper we point out another advantage of systematic sampling over simple random sampling, which have not yet been spelled out in the literature. After a single sample is drawn by a sampling scheme, it is important to check whether the achived sample represents the population well or not. Therefore. a sampling scheme which avoids the possibility of selecting non-preferred samples is desirable. The simulation results are given to illustrate that, in the ordered population, the possibility of selecting non-preferred sample by systematic sampling is lower than that by simple random sampling.