• Communications for Statistical Applications and Methods
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• v.12 no.3
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• pp.759-771
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• 2005

Twin studies are one of the most widely used methods for quantifying the influence of genetic and environmental factors on some traits such as a life span or a disease. In this paper we propose a genetic mixed linear model for twin survival time data, which allows us to separate the genetic component from the environmental component. Inferences are based upon the hierarchical likelihood (h-likelihood), which provides a statistically efficient and simple unified framework for various random-effect models. We also propose a simple and fast computation method for analyzing a large data set on twin survival study. The new method is illustrated to the survival data in Swedish Twin Registry. A simulation study is carried out to evaluate the performance.

• The Korean Journal of Applied Statistics
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• v.11 no.1
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• pp.185-192
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• 1998

A bivariate extension of the two-parameter exponential distribution is proposed as a model for certain problems in system level life testing. In particular, it applies to two-component shared parallel systems having a minimum guarantee time. Various statistical properties of the model are investigated, including maximum likelihood estimators (MLEs), modified MLEs, and unbiased estimators of the parameters and their distributions.

• Journal of the Korean Statistical Society
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• v.30 no.1
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• pp.89-98
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• 2001

Brown and Proschan(1983) introduced a model for imperfect repair. At each failure of a device, with probability p, it is repaired completely or replaced with a new device(perfect repair), and with probability 1-p, it is returned to the functioning state, but it is only recovered to its condition just prior to failure(imperfect repair or minimal repair). In this paper, we limit the number of consecutive minimal repairs by n. We find some useful properties about $\mu$$_{k}$, the expected time between the k-th and the (k+1)-st repair under he assumption that only minimal repairs are performed. Then, we assign cost to each repair and find the value of n which minimized the long-run average cost for a fixed p under the condition that the life distribution F os the device is DMRL.L.

• Journal of the Korean Statistical Society
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• v.24 no.1
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• pp.197-218
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• 1995

We first consider the random censorship model of survival analysis. Efron (1981) introduced two equivalent bootstrap methods for censored data. We propose a new bootstrap scheme, called Method 3, that acts conditionally on the censoring pattern when making inference about aspects of the unknown life-time distribution F. This article contains (a) a motivation for this refined bootstrap scheme ; (b) a proof that the bootstrapped Kaplan-Meier estimatro fo F formed by Method 3 has the same limiting distribution as the one by Efron's approach ; (c) description of and report on simulation studies assessing the small-sample performance of the Method 3 ; (d) an illustration on some Danish data. We also consider the model in which the survival times are censered by death times due to other caused and also by known fixed constants, and propose an appropriate bootstrap method for that model. This bootstrap method is a readily modified version of the Method 3.

• Communications for Statistical Applications and Methods
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• v.11 no.2
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• pp.213-225
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• 2004

A fixed-strike lookback option is an option whose payoff is determined by the maximum (or minimum) price of the underlying asset within the option's life. Under the Black-Scholes framework, the time-t price of an equity asset follows a geometric Brownian motion. Applying the method of Esscher transforms, this paper will derive explicit pricing formulas for fixed-strike lookback call and put options, respectively. In addition, this paper will show a relationship (duality property) between the pricing formulas of the call and put options. Finally, this paper will derive explicit pricing formulas for the fixed-strike lookback options when their underlying asset pays dividends continuously at a rate proportional to its price.

• Communications for Statistical Applications and Methods
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• v.16 no.5
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• pp.731-743
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• 2009

The interval estimation for binomial proportion has been treated practically as well as theoretically for a long time. In this paper we compared the properties of major confidence intervals and summarized current issues for coverage probability and interval length which are the criteria of evaluation for confidence interval. Additionally, we examined the three topics which were considered in using the binomial confidence interval in the field. And finally we discussed the future studies for a low binomial proportion.

• Communications for Statistical Applications and Methods
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• v.13 no.1
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• pp.11-17
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• 2006

The spacing of inspection times in intermittent inspection is of great interest, and several ways for the determination of inspection times have been proposed. In most inspection schemes including equally spaced inspection and optimally spaced inspection, the best inspection times in each inspection scheme depend on the unknown parameter, and we need an initial guess of the unknown parameter for practical use. Thus it is evident that the efficiency of the resulting inspection scheme highly depends on the choice of the initial value. However, since we can obtain some information about the unknown parameter at each inspection, we may use the accumulated information and adjust the next inspection time. In this paper, we study this sequential determination of the inspection times in optimally spaced inspection.

• Journal of the Korea Concrete Institute
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• v.17 no.6 s.90
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• pp.1045-1051
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• 2005

For critical structures and application, where a given reliability must be met, it is necessary to account for uncertainties and variability in material properties, structural parameters affecting the corrosion process, in addition to the statistical and decision uncertainties. This paper presents an approach to the fuzzy arithmetic based modeling of the chloride-induced corrosion of reinforcement in concrete structures that takes into account the uncertainties in the physical models of chloride penetration into concrete and corrosion of steel reinforcement, as well as the uncertainties in the governing parameters, including concrete diffusivity, concrete cover depth, surface chloride concentration and critical chloride level for corrosion initiation. The parameters of the models are regarded as fuzzy numbers with proper membership function adapted to statistical data of the governing parameters and the fuzziness of the corrosion time is determined by the fuzzy arithmetic of interval arithmetic and extension principle

• Journal of Korean society of Dental Hygiene
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• v.18 no.3
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• pp.295-310
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• 2018

Objectives: The purpose of this study is to identify the factors affecting job satisfaction, job stress, turnover intention, work-family and family-work relationship of married dental hygienists with young children. Methods: 242 copies of self-reported questionnaires were analyzed. Statistical analysis of collected data was conducted using the statistical program of Stata 13.0 (StataCorp., College Station, TX, USA). Results: Turnover intention was higher when the child age was lower and the child support and parenting stress were higher. But when working hours were adjustable, the turnover intention was low. Job stress was higher as the position, monthly income and night working hours were higher. Job satisfaction was higher as night work was fewer, work time was adjustable and family life satisfaction was higher. When parenting stress was high, job satisfaction was low and job stress and turnover intention were high. Work-family relationships were more affected by lower monthly income and parents-first child caregivers. Workplace factors affecting the family life were monthly income, caregiver and number of night work. The higher the parenting stress, the greater the mutual influence between family and work life. Age, family life, parenting stress and turnover intention were identified to affect family-work relationship. Parenting stress and job stress were identified to be influential on work-family relationship. Conclusions: Married dental hygienists are leaving the clinical setting due to their marriage and childbirth, or showing the effects on family-work and work-family relationships due to parenting. Efforts should be made to efficiently utilize professional manpower and to improve the psychological and physical working environment surrounding the married dental hygienists.

• International Journal of Human Ecology
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• v.12 no.2
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• pp.133-146
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• 2011

This study evaluates common activity and quality of life in Swedish cohousing units to examine whether Swedish cohousing functions properly or not. A questionnaire survey was fulfilled during the autumn of 2010 in G$\ddot{o}$teborg Sweden. The subjects of study were 12 of 44 cohousing units in Sweden that included 4 of the +40 cohousing and 8 of the mixed-age cohousing. A total of 242 of 353 distributed questionnaires were collected (68.6%) and analyzed by SPSS statistical program. The findings are as follow: 1) General characteristics of the respondents are that they are mostly healthy, evenly aged from age 50s to 70s and highly educated with significant proportions of academics and civil workers. There are more females than males and more singles than cohabitants. 2) The most frequent and preferred common activity is a common meal followed by a coffee meeting. A common dinner, the 'hub of living together' is held almost every day or at least a few times a week. A common meal is considered one of the most important activities because of practical and social advantages in that residents can save time and cooking costs as well as engage in social contact. Referring to evaluation of frequency and content of common activity, more than a half of the respondents prefer the current situation. 3) All of the variables (except health conditions and education level) affect participation in common activity with statistical significance. 4) Most of the respondents indicate a high level of life satisfaction and are willing to recommend others move to cohousing. They agree that there is more mutual support among residents in cohousing units than in a conventional community. In conclusion, Swedish cohousing units function successfully as they have pursued intentional community ideology and most of the residents are proud of their current living situations.