• Communications for Statistical Applications and Methods
• /
• v.24 no.1
• /
• pp.29-41
• /
• 2017

The estimation problem of expected time to failure of units is studied in a discrete set up. A simple step-stress accelerated life testing is considered with a Type-I censored sample from geometric distribution that is a commonly used distribution to model the lifetime of a device in discrete case. Maximum likelihood estimators as well as the associated distributions are derived. Exact, approximate and bootstrap approaches construct confidence intervals that are compared via a simulation study. Optimal confidence intervals are suggested in view of the expected width and coverage probability criteria. An illustrative example is also presented to explain the results of the paper. Finally, some conclusions are stated.

• The Korean Journal of Applied Statistics
• /
• v.26 no.1
• /
• pp.59-70
• /
• 2013

Exit polls failed to estimate the number of seats in the National Assembly for each party in the 2012 General Election, even though they estimated it in interval. Three major broadcast companies jointly carried out exit polls, but made projections independently. The exact methods of projection were not publicly released. This paper proposes confidence intervals for the number of seats in local constituencies using the results of exit polls, and conducted simulation studies to assess the performance of the cofidence intervals. The proposed confidence intervals were applied to the real data of 2012 General Election.

• Communications for Statistical Applications and Methods
• /
• v.15 no.5
• /
• pp.655-666
• /
• 2008

Small sample likelihood based inference for the shape parameter of the inverse Gaussian distribution is the purpose of this paper. When shape parameter is of interest, the signed log-likelihood ratio statistic and the modified signed log-likelihood ratio statistic are derived. Hsieh (1990) gave a statistical inference for the shape parameter based on an exact method. Throughout simulation, we will compare the statistical properties of the proposed statistics to the statistic given by Hsieh (1990) in term of confidence interval and power of test. We also discuss a real data example.

• Environmental and Resource Economics Review
• /
• v.11 no.1
• /
• pp.99-119
• /
• 2002

As an alternative to classical maximum likelihood approach for analyzing dichotomous choice contingent valuation (DCCV) data, this paper develops a Bayesian approach. By using the idea of Gibbs sampling and data augmentation, the approach enables one to perform exact inference for DCCV models. A by-product from the approach is welfare measure, such as the mean willingness to pay, and its confidence interval, which can be used for policy analysis. The efficacy of the approach relative to the classical approach is discussed in the context of empirical DCCV studies. It is concluded that there appears to be considerable scope for the use of the Bayesian analysis in dealing with DCCV data.

• Journal of the Korean Data and Information Science Society
• /
• v.24 no.4
• /
• pp.911-918
• /
• 2013

This study deals with the small sample likelihood based inference for the ratio of two normal variances. The small sample likelihood inference is an approximation method. The signed log-likelihood ratio statistic and the modified signed log-likelihood ratio statistic, which converge to standard normal distribution, are proposed for the normal variance ratio. Through the simulation study, the coverage probabilities of confidence interval and power of the exact, the signed log-likelihood and the modified signed log-likelihood ratio statistic will be compared. A real data example will be provided.

• Journal of Korean Academy of Fundamentals of Nursing
• /
• v.19 no.4
• /
• pp.425-433
• /
• 2012

Purpose: The purpose of this study was to investigate sleep patterns and predictors of excessive daytime sleepiness (EDS) in university students. Methods: Participants were 120 university students who were attending two universities in S-city and C-city. Data were collected from May 20 to June 15, 2012 using self-report questionnaires which included Johns' Epworth Sleepiness Scale, Yi's Sleep Quality Scale, and Beck Depression Inventory. Data were digitalized and analyzed using frequency, percentages, means and standard deviations, Wilcoxon rank sum test, Chi-square test, Fisher's exact test, and multiple logistic regression with SAS 9.0. Results: Mean total sleep time was 6.6 hours on weekdays, 8.1 hours on weekends. Mean sleep latency was 19.1 minutes and the score for mean sleep quality was 22.6. Prevalence of EDS was 12.5%. Depression was significantly different between EDS and Non-EDS students (t=2.17, p=.030). Multiple logistic regression showed that the only factor associated with EDS was depression (adjusted odds ratio of depression=5.33, 95% Confidence Interval=1.49-19.04). Conclusion: Results of this study indicate that university students experience short sleep time, low sleep quality, and common EDS with depression, suggesting that students with complaints of EDS should be completely assessed for depression as well as sleep problems.

• Journal of Oral Medicine and Pain
• /
• v.41 no.4
• /
• pp.188-194
• /
• 2016

Purpose: Burning mouth syndrome (BMS) is ambiguous and enigmatic oral condition. Sleep disturbance is one of the most prevalent complaints of patients with chronic pain. The aim of this study was to estimate general sleep characteristics and propensity in patients with BMS. Methods: A total of thirty BMS patients and thirty healthy control subjects were investigated. Self-reported measures of sleep quality were conducted using two widely used methods; the Pittsburgh Sleep Quality Index (PSQI) and Epworth Sleepiness Scale (ESS). Data were analyzed with one-way ANOVA, chi-square, Fisher's exact test, Kruskal-Wallis test, Holm method with 95% confidence interval and p<0.05 significant level. Results: BMS patients showed more poor sleepers than those in control subjects in both ESS and PSQI test. BMS patients also showed statistically significant poorer sleep quality compared with control subjects in both test. When BMS group were divided into three groups on the basis of numeric rating scale, the higher score subjects had, the more mean rank they had in the PSQI. Conclusions: BMS patients showed up poor sleep characteristics and propensity than control group, and they also showed the more severe the pain was, the worse the sleep quality was.

• The Korean Journal of Physiology and Pharmacology
• /
• v.25 no.6
• /
• pp.545-553
• /
• 2021

Fixed-dose combinations development requires pharmacokinetic drugdrug interaction (DDI) studies between active ingredients. For some drugs, pharmacokinetic properties such as long half-life or delayed distribution, make it difficult to conduct such clinical trials and to estimate the exact magnitude of DDI. In this study, the conventional (non-compartmental analysis and bioequivalence [BE]) and model-based analyses were compared for their performance to evaluate DDI using amlodipine as an example. Raw data without DDI or simulated data using pharmacokinetic models were compared to the data obtained after concomitant administration. Regardless of the methodology, all the results fell within the classical BE limit. It was shown that the model-based approach may be valid as the conventional approach and reduce the possibility of DDI overestimation. Several advantages (i.e., quantitative changes in parameters and precision of confidence interval) of the model-based approach were demonstrated, and possible application methods were proposed. Therefore, it is expected that the model-based analysis is appropriately utilized according to the situation and purpose.

• Molecules and Cells
• /
• v.42 no.2
• /
• pp.161-165
• /
• 2019

Non-small cell lung cancer (NSCLC) is the leading cause of cancer-related deaths worldwide and has high rates of metastasis. Transforming growth factor beta-inducible protein (TGFBI) is an extracellular matrix component involved in tumour growth and metastasis. However, the exact role of TGFBI in NSCLC remains controversial. Gene silencing via DNA methylation of the promoter region is common in lung tumorigenesis and could thus be used for the development of molecular biomarkers. We analysed the methylation status of the TGFBI promoter in 138 NSCLC specimens via methylation-specific PCR and evaluated the correlation between TGFBI methylation and patient survival. TGFBI promoter methylation was detected in 25 (18.1%) of the tumours and was demonstrated to be associated with gene silencing. We observed no statistical correlation between TGFBI methylation and clinicopathological characteristics. Univariate and multivariate analyses showed that TGFBI methylation is significantly associated with poor survival outcomes in adenocarcinoma cases (adjusted hazard ratio = 2.88, 95% confidence interval = 1.19-6.99, P = 0.019), but not in squamous cell cases. Our findings suggest that methylation in the TGFBI promoter may be associated with pathogenesis of NSCLC and can be used as a predictive marker for lung adenocarcinoma prognosis. Further large-scale studies are needed to confirm these findings.

• Journal of Korean Biological Nursing Science
• /
• v.23 no.4
• /
• pp.298-307
• /
• 2021

Purpose: This study aimed to investigate the risk factors for cardiac implantable electronic device (CIED)-related infections within the first post-procedural year after CIED insertion. Methods: This study included 509 adult patients undergoing CIED implantation procedures between January 1, 2011 and December 31, 2015. The data were analyzed by t-test, chi-square test, Fisher's exact test, and logistic regression analysis using SPSS/WIN 23.0. Results: Fifteen infections and 494 non-infections were examined. The CIED-related infection rate was 2.9%; patients with 14 pocket infections and one bacteremia were included in the CIED-related infection. The risk factors of CIED-related infections were the estimated glomerular filtration rate (eGFR) of ≤ 45 mL/min/1.73 m² (Odds ratio [OR]= 4.03, 95% confidence interval [CI],1.15-14.10) and taking a new oral anticoagulant (NOAC) (OR = 4.50, 95% CI 1.09-18.55). Conclusion: These results identified the CIED infection rate and risk factors of CIED-related infection. It is necessary to consider these risk factors before the CIED implantation procedure and to establish the relevant nursing interventions.