• The Korean Journal of Applied Statistics
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• v.17 no.3
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• pp.393-402
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• 2004

We suggest a summary of sample design for the statistical survey of E-commerce to estimate the general trend as well as the market size and investment scale of e-commerce based on the Census on Basic Characteristic of Establishments(CBCE). The sample design of this survey is composed of systematic sampling and modified cut-off method.

• Communications for Statistical Applications and Methods
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• v.16 no.4
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• pp.669-673
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• 2009

When a social scientist prepares to conduct a survey, he/she faces the problem of deciding an appropriate sample size. Sample size is closely connected with cost, time, and the precision of the sample estimate. It is thus important to choose a size appropriate for the survey, but this may be difficult for survey researchers not skilled in a sampling theory. In this study we propose a method to determine a sample size under certain assumptions when the quantity of interest is measured by a Likert scale.

• Journal of the Korean Data and Information Science Society
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• v.25 no.3
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• pp.523-531
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• 2014

Design effect is often used in designing and planning sample surveys and/or in evaluating the efficiency of complex design features of the surveys. In this study, we applied Gabler et al. (2006)'s design effect model to 2013 Consumer behavior survey for food that was carried out by stratified two-stage sampling. Usability and adequacy of the design model to a real survey data are discussed and evaluated.

• Journal of the Korean Geotechnical Society
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• v.16 no.1
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• pp.145-155
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• 2000

Orientation data of discontinuities are of paramount importance for rock slope stability studies because they control the possibility of unstable conditions or excessive deformation. Most orientation data are collected by using linear sampling techniques, such as borehole fracture mapping and the detailed scanline method (outcrop mapping). However, these data, acquired by the above linear sampling techniques, are subjected to bias, owing to the orientation of the sampling line. Even though a weighting factor is applied to orientation data in order to reduce this bias, the bias will not be significantly reduced when certain sampling orientations are involved. That is, if the linear sampling orientation nearly parallels the discontinuity orientation, most discontinuities orientation data which are parallel to sampling line will be excluded from the survey result. This phenomenon can cause serious misinterpretation of discontinuity orientation data because critical information is omitted. In the case study, orientation data collected by using the borehole fracture mapping method (vertical scanline) were compared to those based on orientation data from the detailed scanline method (horizontal scanline). Differences in results for the two procedures revealed a concern that a representative orientation of discontinuities was not accomplished. Equal-area, polar stereo nets were used to determine the distribution of dip angles and to compare the data distribution fur the borehole method versus those for the scanline method.

• The Korean Journal of Applied Statistics
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• v.28 no.6
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• pp.1047-1061
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• 2015

Stratified random sampling is a powerful sampling strategy to reduce variance of the estimators by incorporating useful auxiliary information to stratify the population. Sample allocation is the one of the important decisions in selecting a stratified random sample. There are two common methods, the proportional allocation and Neyman allocation if we could assume data collection cost for different observation units equal. Theoretically, Neyman allocation considering the size and standard deviation of each stratum, is known to be more effective than proportional allocation which incorporates only stratum size information. However, if the information on the standard deviation is inaccurate, the performance of Neyman allocation is in doubt. It has been pointed out that Neyman allocation is not suitable for multi-purpose sample survey that requires the estimation of several characteristics. In addition to sampling error, non-response error is another factor to evaluate sampling strategy that affects the statistical precision of the estimator. We propose new sample allocation methods using the available information about stratum response rates at the designing stage to improve stratified random sampling. The proposed methods are efficient when response rates differ considerably among strata. In particular, the method using population sizes and response rates improves the Neyman allocation in multi-purpose sample survey.

• Proceedings of the Korean Association for Survey Research Conference
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• 2002.11a
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• pp.255-274
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• 2002

We classify rotation sampling designs into two classes. The first class replaces sample units within the same rotation group while the second class replaces sample units between different rotation groups. The first class is specified by the three-way balanced design which is a multi-level version of previous balanced designs. We introduce an extended generalized composite estimator (EGCE) and derive its variance and mean squared error for each of the two classes of design, cooperating two types of correlations and three types of biases. Unbiased estimators are derived for difference between interview time biases, between recall time biases, and between rotation group biases. Using the variance and mean squared error, since any rotation design belongs to one of the two classes and the EGCE is a most general estimator for rotation design, we evaluate the efficiency of EGCE to simple weighted estimator and the effects of levels, design gaps, and rotation patterns on variance and mean squared error.

• Animal Systematics, Evolution and Diversity
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• v.27 no.2
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• pp.151-158
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• 2011

Fish community structure in the Pyeongchanggang River was investigated from April to November 2009. About 900 individuals representing 24 species from eight families at six sites in the Pyeongchanggang River were collected. It was similar to the 2001's survey and it was less than 2006's survey. The Korean endemic species, Zacco koreanus was the most abundant, whereas subdominant species were native species, such as Pungtungia herzi, Zacco platypus, Rhynchocypris kumgangensis and Rhynchocypris oxycephalus. Three endangered species were collected at the sampling area, Acheilognathus signifier (relative abundance [RA] 0.9%), Pseudopungtungia tenuicorpa (RA 1.4%), and Cottus koreanus (RA 3.6%). One natural monument species, Hemibarbus mylodon, was included. According to the analysis of ecological indicator characteristics, the relative proportion of tolerant species was 6.3% (57 individuals), whereas the proportion of sensitive species was 65.9% (593 individuals). Species evenness, richness and diversity indices decreased gradually through the month from April to November during the study. Community indices in Pyeongchanggang River showed a high evenness index (J'>0.6), a low level of species richness (R<3.5) and a medium level of diversity (1.5

• The Journal of Asian Finance, Economics and Business
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• v.5 no.4
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• pp.117-125
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• 2018

As various types of information technology systems are becoming more pervasive than ever, many studies have evaluated the systems from the user perspective. Some of them have used surveys to measure consumers' cognitive responses to the target technology. However, this method may cause problems if the survey participants do not have a useful frame of reference for evaluating an unfamiliar system. To examine this issue, the current study empirically tested the effect of personal product knowledge on the predictability of a behavioral model, such as Technology Acceptance Model. A series of measurement invariance tests as well as multi-group comparison tests were conducted for rigorous examination of the data. Our analysis showed that the variance of attitude that is explained by the two believes (perceived usefulness and ease of use) was relatively small when the survey respondents had lower amount of product knowledge. Moreover, the group had weaker causal relationship between attitude and intention to use the technology, hindering the predictability of the research model. The results indicated that respondents should have a certain amount of knowledge of the target system in order to form accurate beliefs and behavioral decisions. The findings of this study provide important implications on sampling strategies for researchers with new technology.

• Survey Research
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• v.9 no.1
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• pp.43-68
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• 2008

This study compares two instruments for time use study: The time diary and the Experience Sampling Method (ESM), While previous studies show that the ESM and the full-diary are similar with respect to aggregate estimates, No previous study has examined the concordance rates of individual records from both instruments. Based on the subsamples who completed both instruments during the same time period from 500 family studies conducted by the Alfred P. Sloan Center on Parents, Children, and Work at the University of Chicago, we systematically compares the two instruments and evaluates their relative strengths. The results suggest that time diaries provide less biased time use estimates. and that compared to the time diary, the ESM provides a more detailed description of everyday life. The implications of further researches are discussed.

• Journal of Construction Engineering and Project Management
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• v.8 no.1
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• pp.1-9
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• 2018

US transportation agencies are dealing with shrinking budgets, limited work forces, and deteriorating infrastructure. In order to cope with funding uncertainty, state highway agencies are now looking into their own organizations and identifying programs, practices, and processes that have potential for cost saving. A quality assurance (QA) program is an integral part of highway construction and ensures a project's contracted level of quality. The cost of quality (conforming and nonconforming) can constitute a sizable part of total construction cost. As the quality assurance programs evolved, various practices and processes were developed over time and later adopted by state highway agencies. These practices and processes include different QA standards and specifications, varying testing methods, central testing lab vs. on site testing, performance based vs. prescribed quality assurance practices, implementation of innovative quality assurance practices, etc. Therefore, there is an opportunity to assess different QA strategies and recommend those practices that are effective and cost efficient. A national survey was conducted by the authors, which provided a detailed mapping of various QA practices and processes used as part of QA programs and identified areas where agencies can focus on for cost savings. The survey found that QA sampling and testing plans, optimization of sampling plans, optimization of QA standards and specifications, and implementation of innovative test methods and processes are the main areas the agencies should focus to lean the current QA programs.