• The Korean Journal of Applied Statistics
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• v.14 no.1
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• pp.81-90
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• 2001

One of the Repeated survey which estimates variability of population, we can be consider rotation sample survey. There are two kinds of rotation sample survey - onelevel rotation sample survey and multi-level rotation sample survey. In rotation sample survey, Composite estimator is used to measure level or level change of the population. This study suggests Generalized Composite estimator as considering intraclass correlation in multi-level rotation sample survey, and optimal weight minimizing variance of estimator. Numerical example shows efficiency of Generalized Composite estimator as considering intraclass correlation according to the sample unit and change degree of intraclass correlation in the rotation group.

• The Korean Journal of Applied Statistics
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• v.17 no.1
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• pp.61-73
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• 2004

Rotation sampling designs may be classified into two categories. The first type uses the same sample unit for the entire life of the survey. The second type uses the sample unit only for a fixed number of times. In both type of designs, the entire sample is partitioned into a finite number(=G) of rotation groups. This paper is generalization of the first type designs. Since the generalized design can be identified by only G rotation groups and recall level 1, we denote this rotation system as l/G rotation design. Under l/G rotation design, variance and mean squared error (MSE) of generalized composite estimator are derived, incorporating two type of biases and exponentially decaying correlation pattern. Compromising MSE's of some selected l/G designs, we investigate design efficiency, design gap effect, ans the effects of correlation and bias.

• The Korean Journal of Applied Statistics
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• v.15 no.1
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• pp.45-55
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• 2002

The 2-level rotation design based on 3 rotation groups is discussed in view of Monthly Retail Trade Survey conducted by the Bureau of Census in U.S., and composite estimators for population characteristics are concerned. The generalized composite estimators and the recursive composite estimators are presented at 2-level rotation design with design gap and variance formulas for the composite estimators are provided. Also under the response variability related with covariance structure and correlation structure from repeated response, relative efficiencies of the composite estimators are compared.

• The Korean Journal of Applied Statistics
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• v.21 no.3
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• pp.361-375
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• 2008

We propose proper methods to impute the item nonresponse in 4-8-4 rotation sample survey. We consider nonignorable nonresponse mechanism that can happen when survey deals with sensitive question (e.g. income, labor force). We utilize modeling imputation method based on Bayesian approach to avoid a boundary solution problem. We also estimate a interview time bias using imputed data and calculate cell expectation and marginal probability on fixed time after removing estimated bias. We compare the mean squared errors and bias between maximum likelihood method and Bayesian methods using simulation studies.

• Proceedings of the Korean Statistical Society Conference
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• 2004.11a
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• pp.49-54
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• 2004

본 연구에서는 표본 농가의 교체나 무응답으로 인한 데이터의 손실을 최소화하기 위하여 핫덱방법을 적용할 때 필요한 무응답 대체군 형성 방안을 제안하였다. 농가경제조사의 무응답 현황과 특성을 살펴보고, 대체군 형성 방안들을 비교할 수 있는 측도를 제안하였다. 제안된 비교 측도를 이용해서 대체군 형성 방안들을 비교하였다.

• The Korean Journal of Applied Statistics
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• v.6 no.1
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• pp.145-162
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• 1993

We review sampling schemes on successive occasions with partial replacement of units and propose a Rao-Hartley-Cochran(RHC) type's sampling scheme over two successive occasions with probability proportionate to observations on the previous occasion. For comparison of the reviewed and proposed sampling schemes, optimal estimator of population mean on second occasion and its variance are derived. The relative efficiency of the proposed sampling scheme is compared with other equal and unequal probability sampling scheme by theoretical and numerical simulation study. For simulation study, three artificial populations are generated by a time series model. It is observed that RHC type's sampling scheme has small variance and deviation in general.

• Culinary science and hospitality research
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• v.16 no.4
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• pp.1-14
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• 2010

This study is to analyze the difference of perception about Korean traditional food by generations in Busan area. For the analysis of this study, both the cross tabulation analysis and Frequency analysis were used, by choosing the random specimen of investigation from middle and high school students, college students and general people residing in Busan area. The result of the study is as follows. First, the frequency of preference for traditional food is different by generations. Second, Korean traditional food is the most preferred among all generations. Third, menu is decided mainly for a father in the family. Finally, standardized and simplified recipes are needed for busy people. To improve the difference by generation, herbs or seasonings should be added or ingredients should be changed into ones suitable to young generation's taste. It is necessary for future studies to have extended samples nationwide for balanced specimen.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.4
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• pp.156-163
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• 2020

This study was conducted to provide basic data for realistic applicable changes of sirens by identifying the stress due to the currently used sirens and the need for improving siren. The data was collected from an online survey of 267 subjects who voluntarily agreed to join this study from August 2019 to September, 2019. A structured questionnaire was used as a research tool. The results were analyzed by means and standard deviations, percentages and frequency analysis, and independent t-tests using SPSS. For the current workplace emergency siren type, it is believed that the number of hybrid formats was 143, the most negative opinion of the siren is high at 132, so periodic replacement is needed. For contextual stresses, the highest was 4.35 ± 0.94, when the siren was heard during bedtime. In the stress during sleep, which was based on the daily mean number of movements,, a statistically significant difference was shown between groups of 9 or more movements and below 9 movements (p <0.05). The type of siren paramedics wanted was 'soft music' and 'sound of nature'. More than half of 168 people (62.9%) wanted to replace the current siren, and 163 (91.6%) wanted that periodically within 24 months. Therefore, it is necessary to improve the siren.

• Journal of Digital Convergence
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• v.14 no.6
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• pp.467-475
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• 2016

This study examined the impact of departmental trust on departmental development and academic performance in the department affiliated with physical eduction. Furthermore, it investigated the differences of departmental development and departmental trust by gender and school year of the students. Data were analyzed from 313 students in the department affiliated with Physical Education from 6 institutions of a 4-year university located in Seoul, Gyeonggi-do, Incheon, and ChungChong-do. For the research questions, simple linear regression model and two-way multivariate analysis of variance were analyzed. Results indicated that departmental trust had a positive effect on departmental development. But, departmental trust statistically had no effect on academic performance. Sophomore and junior in departmental development were higher than senior. Junior in departmental trust was higher than senior. There was no statistically difference in departmental development and departmental trust by gender.

• Journal of Korea Foresty Energy
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• v.22 no.3
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• pp.1-10
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• 2003

The successional status and potential natural vegetation were examined in the natural deciduous forest in Mt. Chombong area. The examination was based on the subsequent process of generation replacement by understory saplings for the dominant canopy trees within 106 20mx20m square sample plots. The transition matrix model, which was modified from mathematical theory of Markov chain, was employed to analyze the successional status of the study forest. The model suggests that study forest is still seral, and it is considered to be more than 500 years away from the steady state or climax in terms of species composition. The simulations predict a remarkable decrease in the proportion of species composition of the present dominant Quercus mongolica and Kalopanax pictus from current 42.6% and 8.1% to less than 13.3% and 0.5%, respectively, at the steady state. On the contrary, the proportions of Abies holophylla, Acer mono, Fraxinus mandshurica, Tilia amurensis, and Acer pseudo-sieboldianum will increase at the steady state. The change of predicted composition ratio was generally coincide with the result of tolerance index to be compared with the study model. The hypothesis and sensitivity of the model were also discussed to evaluate the applicability to the real situation. The overall results indicated that the present dynamics of the forest must reflect the seral state due to previous disturbance mainly by human related interference.