• Journal of the Korean Data and Information Science Society
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• v.13 no.1
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• pp.67-77
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• 2002

We propose the Bayesian testing for the equality of K-exponential populations means with Type-II censored data. Specially we use the fractional Bayesian factors suggested by O'Hagan (1995) based on the noninformative priors for the parameters. And, we investigate the usefulness of the proposed Bayesian testing procedures via both real data analysis and simulations and compare the classical likelihood ratio(LR) test with the proposed Bayesian test.

• The Journal of the Acoustical Society of Korea
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• v.26 no.5
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• pp.194-198
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• 2007

In this paper, we apply a discriminative weight training to a statistical model-based voice activity detection(VAD). In our approach, the VAD decision rule is expressed as the geometric mean of optimally weighted likelihood ratios(LRs) based on a minimum classification error(MCE) method which is different from the previous works in that different weights are assigned to each frequency bin which is considered more realistic. According to the experimental results, the proposed approach is found to be effective for the statistical model-based VAD using the LR test.

• The Journal of the Acoustical Society of Korea
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• v.29 no.1
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• pp.76-81
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• 2010

In this paper, we propose a novel approach to improve the performance of a statistical model-based voice activity detection (VAD) which is based on the second-order conditional maximum a posteriori (CMAP). In our approach, the VAD decision rule is expressed as the geometric mean of likelihood ratios (LRs) based on adapted threshold according to the speech presence probability conditioned on both the current observation and the speech activity decisions in the pervious two frames. Experimental results show that the proposed approach yields better results compared to the statistical model-based and the CMAP-based VAD using the LR test.

• Communications for Statistical Applications and Methods
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• v.10 no.3
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• pp.749-764
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• 2003

In this paper we explain that normal theory likelihood-ratio tests(z, t, $x^2$. F) for mean(s) or variance(s) can be geometrically related to volume of difference of two joint pdf's. One is an estimated joint pdf under null parameter space $\omega$ and the other is an estimated joint pdf under full parameter space $\Omega$. For explanations, ‘distance between two distributions’ is defined. We study properties of it, and derive some results on the distance between two multivariate normal distributions.

• Korea Trade Review
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• v.41 no.5
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• pp.373-389
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• 2016

This study mainly investigates the port SOC's impact on trade volume. In order to investigate the relationships between port SOC and trade volume, we did the empirical analysis using panel data regression and fixed effects model. The total period of 97 years and 1,082 ports' information were applied to panel data and regression model. According to the results, the coefficients of development of container berth, development of bulk berth, maintenance of port, the jetty facilities like breakwater have positive(+) impact on the dependent variable, the trade volume. Especially, the jetty facilities show a strongly positive impact on trade volume. On the other hand, the development of new port and navigation facilities like lighthouse have a negative(-) impact. In examining Hausman test and LR test, the fixed effect model is statistically more appropriate than the random effect model for this study.

• The Journal of the Acoustical Society of Korea
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• v.30 no.6
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• pp.324-329
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• 2011

In this paper, we propose a novel approach to improve the performance of a statistical model-based voice activity detection (VAD) which is based on the conditional maximum a posteriori (CMAP) with deviation. In our approach, the VAD decision rule is expressed as the geometric mean of likelihood ratios (LRs) based on adapted threshold according to the speech presence probability conditioned on both the speech activity decisions and spectral deviation in the pervious frame. Experimental results show that the proposed approach yields better results compared to the CMAP-based VAD using the LR test.

• Journal of Korean Society of Transportation
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• v.30 no.6
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• pp.3-12
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• 2012

Additive willingness-to-pay (WTP) for leisure-travel time saving focused on the Iksan-Pohang Expressway and the Donghae Expressway was surveyed during the summer months to estimate the value of travel-time savings (VTTS) for non-business leisure trips. Travelers traveling between 2 and 3 hours on Iksan-Pohang Expressway had WTP of 723 won per 10 minutes of leisure-travel time savings and those traveling between 3 and 4 hours on Donghae Expressway had WTP of 854 won per the same. Based on this survey, we learned that WTP in leisure travel time savings increased with the total travel time. 300 effective samples for each expressway were collected, and estimation was separately conducted on the basis of Cox test.

• Asian Pacific Journal of Cancer Prevention
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• v.16 no.14
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• pp.5889-5897
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• 2015

Background: The performance of combined testing visual inspection with acetic acid (VIA) and cervical cytology tests might differ from one setting to another. The average estimate of the testing accuracy across studies is informative, but no meta-analysis has been carried out to assess this combined method. Objective: The objective of this study was to estimate the average sensitivity and specificity of the combined VIA and cervical cytology tests for the detection of cervical precancerous lesions. Materials and Methods: We conducted a systematic review and a meta-analysis, according to the Cochrane Handbook for Systematic Review of Diagnostic Test Accuracy. We considered two cases. In the either-positive result case, a positive result implies positivity in at least one of the tests. A negative result implies negativity in both tests. In the both-positive case, a positive result implies having both tests positive. Eligible studies were identified using Pubmed, Embase, Website of Science, CINHAL and COCRANE databases. True positive, false positive, false negative and true negative values were extracted. Estimates of sensitivity and specificity, positive and negative likelihood (LR) and diagnostic odds ratios (DOR) were pooled using a hierarchical random effect model. Hierarchical summary receiver operating characteristics (HSROC) were generated and heterogeneity was verified through covariates potentially influencing the diagnostic odds ratio. Findings: Nine studies fulfilled inclusion criteria and were included in the analysis. Pooled estimates of the sensitivities of the combined tests in either-positive and both-positive cases were 0.87 (95% CI: 0.83-0.90) and 0.38 (95% CI: 0.29-0.48), respectively. Corresponding specificities were 0.79 (95% CI: 0.63-0.89) and 0.98 (95% CI: 0.96-0.99) respectively. The DORs of the combined tests in either-positive or both-positive result cases were 27.7 (95% CI: 12.5-61.5) and 52 (95% CI: 22.1-122.2), respectively. When including only articles without partial verification bias and also a high-grade cervical intraepithelial neoplasia as a threshold of the disease, DOR of combined test in both-positive result cases remained the highest. However, DORs decreased to 12.1 (95% CI: 6.05-24.1) and 13.8 (95% CI: 7.92-23.9) in studies without partial verification bias for the combined tests in the either-positive and both-positive result cases, respectively. The screener, the place of study and the size of the population significantly influenced the DOR of combined tests in the both-positive result case in restriction analyses that considered only articles with CIN2+ as disease threshold. Conclusions: The combined test in the either-positive result case has a high sensitivity, but a low specificity. These results suggest that the combined test should be considered in developing countries as a primary screening test if facilities exist to confirm, through colposcopy and biopsy, a positive result.

• Korea Trade Review
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• v.42 no.2
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• pp.277-296
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• 2017

More than 95% of imports and exports in the World are being transported by vessels. In other words, marine transportation accounts for a large portion of share in the world trade. The purpose of this study is to analyze factors of seaborne trade volume according to items affecting on the world economy. This study conducted a linear regression analysis between seaborne trade volume and the world economy (world GDP) to estimate the correlation between them. Panel data analysis and random effects model analysis have been applied to examine the effect of seaborne trade volume. For this study, the seaborne trade volume is categorized into 10 items, and estimated how much global GDP will be affected when the trade volume changes. In addition, the granger causality test was conducted to verify the relationship between seaborne trade volume and the world GDP. As a result, seaborne trade volume and the world GDP were mutually influenced each other. However, seaborne trade volume affects the world economy more significantly. The items affecting world economic growth include petroleum products, crude oil, chemical products, and so on. The estimated value of the coefficients of petroleum products, crude oil and chemical products were 1.014, 1.013 and 1.010, respectively. The estimated value 1.014 of petroleum products means that the growth rate is 1.014 times higher than the current world GDP growth rate when the seaborne trade volume of petroleum products increased by one unit Lastly, this study examines the seaborne trade volume of 10 categories and then verifies whether the growth rate of world GDP will increase when the volume of seaborne trade increased. This study is expected to provide policy-makers with useful information about formulating policies related to international trade.

• Tuberculosis and Respiratory Diseases
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• v.57 no.5
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• pp.419-424
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• 2004

Background : Although bronchodilator reversibility testing is widely performed to diagnose asthma or COPD, there is debate upon its usefulness and methods to differentiate asthma from COPD. The purpose of this study is to elucidate the role of bronchodilator reversibility testing in differentiating asthma from COPD and to confirm which method is better at evaluating bronchodilator reversibility. Methods : 26 asthma patients and 31 COPD patients were reviewed retrospectively. Spirometry was performed before and after bronchodilator inhalation to get $FEV_1$, FVC. To evaluate bronchodilator reversibility, the increase in $FEV_1$ or FVC was expressed as three methods, 'percentage of the baseline value', 'percentage of the predicted value', or 'absolute value'. Area under the ROC curve was measured to compare the three methods. In addition, the criteria of American Thoracic Society (ATS) for bronchodilator reversibility were compared to those of European Respiratory Society (ERS). Results : 1. In differentiating asthma from COPD, 'percentage of the predicted value', or 'absolute value' method was useful but 'percentage of the baseline value' was not. However, the ability to differentiate was weak because areas under the ROC curves by all methods were less than 0.75. 2. The criteria of ERS were superior to those of ATS for bronchodilator reversibility to differentiate asthma from COPD because likelihood ratio (LR) of a positive test by ERS criteria was greater than ATS criteria and because LR of a negative test by ERS criteria was less than ATS criteria. Conclusion : In differentiating asthma from COPD, bronchodilator reversibility testing has a weak role and should be considered as an adjunctive test.