• Title, Summary, Keyword: 분포 가설

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A study on change-points in simple linear regression (단순선형회귀에서의 변화점에 대한 연구)

  • 정광모;한미혜
    • The Korean Journal of Applied Statistics
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    • v.5 no.1
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    • pp.29-39
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    • 1992
  • A testing and estimation procedure is considered for changes at unknown time point in simple linear regression model. A test statistic of quadratic form is suggested. We also discuss the asymptotic distribution and its level control. The proposed method is compared with the likelihood ratio test through a example.

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Distribution of Benthic Diatoms in Tidal Flats of Hampyeong Bay, Korea (함평만 갯벌의 저서규조류 분포 특성)

  • Lee, Hak-Young;Jung, Myoung-Hwa
    • Korean Journal of Environmental Biology
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    • v.29 no.1
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    • pp.17-22
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    • 2011
  • The distributional pattern of benthic diatoms in tidal flats of Hampyeong Bay, Korea, was studied from January to October in 2009. As benthic diatoms of Hampyeong Bay tidal flats, 45 species were identified, and the most dominant species was Paralia sulcata. The most diverse flora was observed at Gaip and Songseok sites in April with 22 species, and the least at Hyeonhwa site in January. The ranges of chlorophyll-a concentration in tidal flats were 21.2~31.8 mg$m^{-2}$ at Hyeonhwa site, 23.6~35.4 mg $m^{-2}$ at Gaip site, and 24.2~34.3 mg $m^{-2}$ at Songseok site. The concentrations of pheopigment ranged between 25.3 and 45.2 mg$m^{-2}$. The standing crops of benthic diatoms showed highest density in April and lowest in January, February, and October. The cell volumes of benthic diatoms were highest in April. The taxa and biomass of benthic diatoms showed correlations with temperature. On temperature variables, the benthic diatoms showed optimal occurrences at the range of $14{\sim}17^{\circ}C$.

Bayesian Testing for the Equality of K-Exponential Populations (K개 지수분포의 상등에 관한 베이지안 다중검정)

  • Moon, Kyoung-Ae;Kim, Dal-Ho
    • Journal of the Korean Data and Information Science Society
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    • v.12 no.1
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    • pp.41-50
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    • 2001
  • We propose the Bayesian testing for the equality of K-exponential populations means. Specially we use the intrinsic Bayesian factors suggested by Beregr and Perrichi (1996,1998) based on the noninformative priors for the parameters. And, we investigate the usefulness of the proposed Bayesian testing procedures via simulations.

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Cyclicality of Inter-Industry Wage Gaps and Segmented Labor Market Hypotheses (산업간 임금격차의 경기변동상 변화 패턴과 분단노동시장 가설)

  • Shin, Donggyun
    • Journal of Labour Economics
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    • v.26 no.3
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    • pp.77-114
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    • 2003
  • Analyses of the special data sets constructed from the National Longitudinal Survey of Youth and the Panel Study of Income Dynamics reveal that, compared with an annual wage measure, survey week wages are significantly counter-cyclically biased due to selecting workers with strong labor market attachment. We also find that survey week wages are more counter-cyclically biased in high-wage industries than in low-wage industries, that is, inter-industry gaps of survey week wages are counter-cyclically biased. Unlike existing longitudinal studies, the current study concludes that real wages are much more procyclical in high-wage industries than in low-wage industries, which is attributed to our adoption of annual wages that is less subject to the selectivity bias. Our finding is consistent with the empirical regularity that real wages are much more procyclical for men than for women, as men are overrepresented in industries with greater real wage procyclicalities. Overall, current results do not support the predictions of segmented labor market theories for the cyclicality of real wages.

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Word Sense Similarity Clustering Based on Vector Space Model and HAL (벡터 공간 모델과 HAL에 기초한 단어 의미 유사성 군집)

  • Kim, Dong-Sung
    • Korean Journal of Cognitive Science
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    • v.23 no.3
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    • pp.295-322
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    • 2012
  • In this paper, we cluster similar word senses applying vector space model and HAL (Hyperspace Analog to Language). HAL measures corelation among words through a certain size of context (Lund and Burgess 1996). The similarity measurement between a word pair is cosine similarity based on the vector space model, which reduces distortion of space between high frequency words and low frequency words (Salton et al. 1975, Widdows 2004). We use PCA (Principal Component Analysis) and SVD (Singular Value Decomposition) to reduce a large amount of dimensions caused by similarity matrix. For sense similarity clustering, we adopt supervised and non-supervised learning methods. For non-supervised method, we use clustering. For supervised method, we use SVM (Support Vector Machine), Naive Bayes Classifier, and Maximum Entropy Method.

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An Improved Method to Recognize Range Profiles Using Statistical Hypothesis Test and Principal Component Analysis (가설검정 및 주값분해를 이용한 개선된 거리측면도 식별 기법)

  • Choi, In-O;Jung, Joo-Ho;Kim, Kyung-Tae;Park, Sang-Hong
    • 한국정보기술학회논문지
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    • v.15 no.1
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    • pp.115-122
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    • 2017
  • Range profile (RP) is an one-dimensional (1D) distribution of the scatterer of a target, projected onto the radar line-of-sight. Because RP provides the information of the 1D distribution of the target regardless of the weather and day-night conditions and automated algorithms can be designed for the recognition of RP, it can be used for the recognition purpose very effectively. However, due to the severe fluctuation of RP depending on the aspect angle and the operating frequency, a large amount of training database is required and in addition, a compression method of feature vectors is required to remove redundancies and separate targets in the feature space. This paper proposes an efficient compression method to solve these problems. The proposed method is a combination of the statistical hypothesis testing and the principal component analysis applied to the central moment of RP. In classification simulations using the targets modeled by using the CAD data of the real target, the proposed method provided higher classification results with further compressed data than did the existing method.

The Methodology for Environmental Risk Assessments of Non-target Organisms (Insects) on LM Rice (LM벼에 영향을 받는 비표적 생물체(곤충)에 대한 환경위해성 평가 (ERA) 방법)

  • Yi, Hoonbok;Kim, Hyun-jung;Na, Sumi
    • Korean Journal of Environment and Ecology
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    • v.30 no.4
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    • pp.712-723
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    • 2016
  • This paper is to suggest the methods about the environmental risk assessment (ERA) based on non-target insect species for LM rice crop produced by biotechnology. We used some data by the picture dictionary of agricultural pests in Korea, some books for ERA or rice pest ecology, articles about rice ecology, and internet sites and many specialists gave us good advice for this ERA system. We found about 140 insect species using rice crop as their habitat and we discriminated herbivores into Sap feeder, Grain feeder, Defoliator, and Pollen feeder according to their food functional group. We also clarified the potential damage possibility of insect species from LM rice crop. Then, we ranked 10 non-target insect species (Baliothrips biformis, Laodelphax striatellus, Nilaparvata lugens, Mythimna separata, Cnaphalocrocis medinalis, Cletus schmidti Kiritshenko, Scotinophara lurida, Nilaparvata bakeri, Oxya chinensis, Agromyza oryzae) with giving some scores using Geographic distribution, Habitat specialization, Prevalence on crop, Abundance. We showed some environmental risk hypotheses about herbivore, predator, and parasitoid, and infered the impacts of non-target species on LM rice crop. Conclusively, we want to serve this methodology to build the biosafety system from biotechnology crops, and the methodology is to keep public health, sustain the biodiversity, and conserve the natural ecosystems.

Comparison of Some Nonparametric Statistical Inference for Logit Model (로짓모형의 비모수적 추론의 비교)

  • 정형철;김대학
    • The Korean Journal of Applied Statistics
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    • v.15 no.2
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    • pp.355-366
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    • 2002
  • Nonparametric statistical inference for the parameter of logit model were examined. Usually nonparametric approach is milder than parametric approach based on normal theory assumption. We compared the two nonparametric methods for legit model, the bootstrap and random permutation in the sense of coverage probability. Monte Carlo simulation is conducted for small sample cases. Empirical power of hypothesis test and coverage probability for confidence interval estimation were presented for simple and multiple legit model respectively. An example were also introduced.

An Empirical Test for the Relationship among Maturity, Volume and Volatility in the Korean Stock Index Futures Market (한국주가지수선물시장에 있어서 만기, 거래량, 그리고 변동성간의 관계에 관한 실증연구)

  • Seo, Sang-Gu;Um, Cheol-Jun;Kang, In-Cheol
    • The Korean Journal of Financial Management
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    • v.16 no.1
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    • pp.193-222
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    • 1999
  • 본 연구는 한국주가지수선물시장에 있어서 1996년 5월부터 1998년 6월까지의 기간동안에 상장되어 실질적으로 거래된 각 주가지수선물 종목별 가격 및 거래량자료를 이용하여 만기까지의 기간, 거래량 그리고 가격변동성간의 체계적인 관계를 검증하였다. 즉, 주가지수선물의 종목들이 만기일에 접근함에 따라 거래량은 어떻게 변동하는가, 그리고 변동성은 어떻게 변동하는가를 실증적으로 검증한 것이다. 검증된 실증결과를 요약하면 다음과 같다. 첫째, 주가지수선물시장에 있어서 거래되는 종목들은 만기까지의 기간과 거래량간에 유의적인 음(-)의 관계가 확인되었고, 이는 만기일에 정근함에 따라 거래량은 증가하는 행태를 갖는다는 것이 일반적인 현상임을 알 수 있었다. 둘째, 주가지수선물시장에서 거래된 종목들에 있어서 동시적 거래량과 변동성간에는 유의적인 양(+)의 관계가 성립함에 따라 혼합분포가설을 주장한 Clark(1973)의 연구결과를 어느 정도 지지하는 증거를 발견하였다. 셋째, 주가지수선물시장에 있어서 만기까지의 기간과 변동성간에는 유의적인 음(-)의 관계가 존재한다는 것을 확인할 수 없었다 즉, 만기일에 접근함에 따라 가격변동성이 증가한다는 만기 효과가설을 지지하는 증거를 한국주가지수선물시장에서는 발견할 수 없었다.

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Meta-analysis of the effects of TPM activity factors on Corporate performance (TPM 활동요인이 기업성과에 미치는 영향에 대한 메타분석)

  • Yeon, Keyong-Hwa
    • Journal of Digital Convergence
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    • v.16 no.2
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    • pp.151-156
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    • 2018
  • The purpose of this study is to conduct a meta-analysis of 18 papers that can be verified among the papers on the subject of TPM. Five hypotheses were set for the analysis and meta - analysis was carried out with CMA as presented in each research paper. As a result of analysis, I-square value is more than 75% in four hypotheses. Therefore, the null hypothesis that the size of the population effect is the same for all studies was rejected. The reason for the heterogeneity is that the research characteristics such as the distribution of the respondents, the study conditions, the study period, and the study area are different. In this case, a summary statistic of the individual studies that can be classified according to the characteristics of the research is needed to analyze the effect size difference. However, individual studies do not provide a summary statistic that can classify the effect differences, so it is not possible to analyze the causes of heterogeneity.