• Journal of Preventive Medicine and Public Health
• /
• 제54권3호
• /
• pp.166-172
• /
• 2021

Traditional epidemiological assessments, which mainly focused on evaluating the statistical association between two major components-the exposure and outcome-have recently evolved to ascertain the in-between process, which can explain the underlying causal pathway. Mediation analysis has emerged as a compelling method to disentangle the complex nature of these pathways. The statistical method of mediation analysis has evolved from simple regression analysis to causal mediation analysis, and each amendment refined the underlying mathematical theory and required assumptions. This short guide will introduce the basic statistical framework and assumptions of both traditional and modern mediation analyses, providing examples conducted with real-world data.

• 한국지구과학회지
• /
• 제18권6호
• /
• pp.515-521
• /
• 1997

난지도 매립장 매립물의 특성을 조사하기 위해서 중력, 자력, LandSat TM 열적외선 밴드 자료, 매립장의 표면에서 측정한 침하량 자료 등을 다변량 통계분석기법을 응용하여 분석하였다. 분석에 이용한 자료들은 각기 상이한 깊이에 관한 정보를 제공하기 때문에 측정된 총 자력자료와 중력자료는 자극화변환된 자력이상과 매립장의 3차원 밀도분포로 각기 전환하였으며, 본 연구에서는 이 중 매립장의 상부층에 관한 정보를 이용하였다. 통계분석은 침하량 측정 지점들을 대상으로 수행하였으며, 이들 지점에서의 자극화변환 자력이상, 매립물의 밀도, LandSat TM 열적외선 밴드 값들은 내삽방법을 이용하여 구하였다. 자료분석에 사용한 다변량 통계분석 기법은 개체간의 기하학적인 거리를 이용하여 군집화하는 집락분석으로, 개체간의 거리 계산시 각 자료간의 상이한 측정단위가 주는 효과를 제거하기 위해서 사전에 표준화를 실시하였다. 군집화는 체계적 군집화 방법을 이용하여 수행하였다. 물리적 특성을 바탕으로 분류된 최적의 군집수는 수상도에서 나타난 결과에 따르면 총 6개의 군집으로 나타났다. 본 연구의 결과는 통합된 지구물리자료에 다변량 통계분석 기법을 적용함으로써 복합적 인 쓰레기 매립장의 특성 규명이 가능함을 시사한다.

• The Journal of Korean Physical Therapy
• /
• 제1권1호
• /
• pp.27-45
• /
• 1989

This study aims at helping cerebrally palsied children to overcome and minimize their sufferings, inducing them to perform ordinary activities of daily living for themselves by coducting ADL Tests which are fundamental activities in daily life and presenting treatment plan for their overall rehabilitation and basic data for achieving the training objective. For that purpose, 173 cerebrally palsied children were selected and given ADL performance Tests from Dec. 1987 to Oct. 1988 and the following results were obtained. 1. Correlation coefficients for each ADL category indicated significant statistical value at .01 level. 2. Correlation coefficient between school-year variable and ADL category variable was significant at .01 level. 3. Correlation between age variable and ADL variable category proved significant at .01 level as well. 4. Correlation coefficients between each category in terms of functional state of extremities were significant at .01 level. 5. The difference in ADL achievements between each category by school year were as follows ; 1) In the category of meeting nature's tall, the age span of more than 4 school years showed statistical significance. 2) In the category of putting off and on clothing, the age span of 3 school years indicated statistical significance. 3) In taking meals statistical significance was found in the age span of 4 school years. 4) In finger movements the age span of more the 4 school years indicated statistical significance. 5) In walking activities statistical significance was noticed in the age span of 2 or 3 school years. Besides, in category by school year, and exceptional case was noticed that the 6th graders were lower than the 5th graders in self-reliance rate. 6. the difference in ADL achievements by type of palsy, children of triplegia were the lowest, while those of monoplegia were the highest. 7. The difference in ADL achievements by kind of palsy, patients of athetosis showed lower rate of self-reliance than those of spasticity, and particularly the latter showed a high rate of self-reliance in taking meals$(83.5\%)$. The former were relatively low in self-reliance and lowerst in meeting nature's call $(59.8\%)$.

• Communications for Statistical Applications and Methods
• /
• 제29권5호
• /
• pp.547-559
• /
• 2022

For a chi-squared test, which is a statistical method used to test the independence of a contingency table of two factors, the expected frequency of each cell must be greater than 5. The percentage of cells with an expected frequency below 5 must be less than 20% of all cells. However, there are many cases in which the regional expected frequency is below 5 in general small area studies. Even in large-scale surveys, it is difficult to forecast the expected frequency to be greater than 5 when there is small area estimation with subgroup analysis. Another statistical method to test independence is to use the Bayes factor, but since there is a high ratio of data dependency due to the nature of the Bayesian approach, the low expected frequency tends to decrease the precision of the test results. To overcome these limitations, we will borrow information from areas with similar characteristics and pool the data statistically to propose a pooled Bayes test of independence in target areas. Jo et al. (2021) suggested hierarchical Bayesian pooling models for small area estimation of categorical data, and we will introduce the pooled Bayes factors calculated by expanding their restricted pooling model. We applied the pooled Bayes factors using bone mineral density and body mass index data from the Third National Health and Nutrition Examination Survey conducted in the United States and compared them with chi-squared tests often used in tests of independence.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 2001년도 하계학술대회 논문집 C
• /
• pp.1606-1608
• /
• 2001

In connection with the monitoring of the insulation degradation of the large power apparatus, a statistical treatment, such as phase resolved partial discharge analysis (PRPDA) has been established for the on-line monitoring system during the past two decades. However, it has shown some inconveniences to distinguish the nature of the PD source in power apparatus. In this regard, a novel approach based on the chaotic analysis(CAPD) is proposed describing the fundamental ideas, outcomes and different view points from conventional PRPDA. In order to make a model for the possible defects causing sudden failures in service, several types of specimen were prepared. And partial discharge signals, originated from those samples, were measured and analyzed by means of PRPDA and CAPD respectively. In this paper, it seems that the correlation between the consecutive PD pulses depending on the nature of PD could be investigated by CAPD. Therefore, it could be considered that the nature of PD source can be distinguished more distinctively when the PRPDA is combined with CAPD.

• Current Applied Physics
• /
• 제18권11호
• /
• pp.1174-1181
• /
• 2018

In nanomagnetism, one of the crucial scientific questions is whether magnetic behaviors are deterministic or stochastic on a nanoscale. Apart from the exciting physical issue, this question is also of paramount highest relevance for using magnetic materials in a wealth of technological applications such as magnetic storage and sensor devices. In the past, the research on the stochasticity of a magnetic process has been mainly done by macroscopic measurements, which only offer ensemble-averaged information. To give more accurate answer for the question and to fully understand related underlying physics, the direct observation of statistical behaviors in magnetic structures and magnetic phenomena utilizing advanced characterization techniques is highly required. One of the ideal tools for such study is a full-field soft X-ray microscope since it enables imaging of magnetic structures on the large field of view within a few seconds. Here we review the stochastic behaviors of various magnetic processes including magnetization reversal process in thin films, magnetic domain wall motions in nanowires, and magnetic vortex formations in nanodisks studied by full-field soft X-ray microscopy. The origin triggering the stochastic nature witnessed in each magnetic process and the way to control the intrinsic nature are also discussed.

• 한국조경학회지
• /
• 제37권5호
• /
• pp.1-12
• /
• 2009

본 연구의 목적은 국립공원 내에 자연친화적인 공원시설의 설계와 설치를 위한 정책방향을 제시하는 것이다. 이를 위해서 국내 외 친환경건물 인증제도와 관련 연구에 대한 고찰을 통해 입지, 설계와 설치, 운영과 관리부분별로 자연친화성 평가지표를 개발하였다. 본 연구에서는 19개 국립공원의 26개 공원사무소에서 실제 시설을 관리하고 있는 공원관리자 79명을 대상으로 한 설문조사를 통해 자연친화성 평가를 위한 자료를 수집하였다. 분석방법은 기술분석, 집단간 평균의 차이분석, 다차원척도법, 요인분석을 활용하였다. 분석결과, 1) 자연친화성 평가지표들 간의 상대적 중요도를 산정한 결과, 시설의 입지 관련지표의 중요도가 가장 높게 나타났다. 2) 공원시설의 자연친화성 수준에 대한 평가 결과, 입지 관련 지표들의 자연친화성 수준이 가장 높게 나타난 반면, 시설의 설계 및 설치 관련 지표들의 수준이 낮게 평가되었다. 특히, 에너지 효율화와 관련된 지표들의 평가값이 가장 낮게 나타났다. 3) 시설별로 보면, 대피소의 자연친화성이 가장 높게 나타난 반면, 휴게소의 자연친화성이 가장 떨어지는 것으로 평가되었다. 4) 전반적으로 볼 때, 설악산, 오대산, 태안해안국립공원의 공원시설에 대한 자연친화성 수준이 높게 나타난 반면, 경주와 속리산 국립공원의 자연친화성 수준은 떨어지는 것으로 평가되었다. 본 연구 결과는 자원절약 및 자연생태계와 공원자원을 보존하고 탐방객의 편리한 이용을 위한 자연친화적인 공원시설 설치를 위한 권고기준을 마련하는데 활용될 수 있을 것이다.

• 한국경영과학회:학술대회논문집
• /
• 한국경영과학회 2000년도 추계학술대회 및 정기총회
• /
• pp.251-254
• /
• 2000

In the knowledge-based economy, technological capability is critical for the survival and growth of firms. Technological capability differs across firms depending on the structural and environmental conditions. In nature, the evaluation of technological capability is an intractable task and thus previous studies often employ such proxy measures as patent, productivity, or profitability. In this research, we define technological capability as a combination of the above three measures and investigate, by using the multi-variate statistical analysis, the characteristics of technological capability of electronics/IT firms of Korea. We first propose a taxonomy in which firms are classified into four clusters based on the differences in the nature of technological capability. Then, across clusters, we comparatively analyze the relationship between technological capability and structural/environmental factors of firms. Finally, the implications of empirical findings will be discussed. This study is a small-scale, descriptive one but will be extended and elaborated by augmenting the database and/or incorporating more variables.

• 대한한의학회지
• /
• 제22권4호
• /
• pp.114-120
• /
• 2001

Objectives : Man adapts himself to nature, so accordingly as he grows up, changes of body composition appear. This study measured the changes of body compositions on the ground of Sasang constitution and seasons Methods : 253 middle school students who live in Busan were studied from the 20th of March, 1999 to the 20th of March, 2001. We measured height and body compositions with Inbody 3.0, six times during that period. Results : According as they grew up, total body water, muscle area, body weight, BMI (Body Mass Index), BMR (Basal Metabolic Rate), ACM (Arm Muscle Circumference), and BCM (Body Cell Mass) increased, but fat body weight ratio decreased. From March to June, total body water, muscle area, height, ACM, and BCM increased. From September to December fat body weight, fat body weight ratio, waist hip ratio increased as compared with other seasons. Height of Soyangin and BMI of both Soyangin and Taeumin increased more than those of other groups, with statistical significance Conclusions : The growth of man is adapting oneself to changes of nature, and it corresponds to the theory of (correspondence between man and universe).

• 동력기계공학회지
• /
• 제14권6호
• /
• pp.61-66
• /
• 2010

Engineering asset management (EAM) requires the accurate assessment of current and the prediction of future asset health condition. Suitable mathematical models that are capable of predicting time-to-failure and the probability of failure in future time are essential. In general reliability models, lifetime of component and system is estimated using failure time data. This paper deals with the reliability assessment of elevators using life of main components. Especially this work is concerned with the stochastic nature of life of elevator components. First, we investigate the Weibull statistical analysis of lifetime data for the components. The final goal is to establish the mathematical model for reliability assessment. This work provides more perspectives to future research in the fields of reliability and maintainability.