• Journal of the Korean Statistical Society
• /
• v.11 no.2
• /
• pp.77-87
• /
• 1982

The choice if constants that define a life testing procedure is considered in terms of the test termination time (censoring time) and the number of items to be tested subject to a given range of variance of the expected life time, where the failure time of life testing is exponentially distributed.

• Journal of Ocean Engineering and Technology
• /
• v.24 no.6
• /
• pp.97-102
• /
• 2010

This paper deals with the variability of short term creep rupture time based on previous creep rupture tests and the statistical methodology of the creep life prediction. The results of creep tests performed using constant uniaxial stresses at 600, 650, and $700^{\circ}C$ elevated temperatures were used for a statistical analysis of the inter-specimen variability of the short term creep rupture time. Even under carefully controlled identical testing conditions, the observed short-term creep rupture time showed obvious inter-specimen variability. The statistical aspect of the short term creep rupture time was analyzed using a Weibull statistical analysis. The effect of creep stress on the variability of the creep rupture time was decreased with an increase in the stress level. The effect of the temperature on the variability also decreased with increasing temperature. A long term creep life prediction method that considers this statistical variability is presented. The presented method is in good agreement with the Lason-Miller Parameter (LMP) life prediction method.

• Communications for Statistical Applications and Methods
• /
• v.10 no.3
• /
• pp.679-694
• /
• 2003

The purpose of this paper is to develop the Index of Balanced Life from the Korean life style. This paper presents How Koreans live for 24 hours a day, generally. The Index of Life Style is composed of necessary life, duty life and leisure life. Specifically, this paper considers moving time of activity between indexes of balanced life. We suggest that there is a difference among the characteristics, i.e., a sex, week, state of student and region that are explained by analyzing the exploratory data. Thereafter we obtain the statistical inference from each characteristic table.

• The Korean Journal of Applied Statistics
• /
• v.2 no.2
• /
• pp.61-78
• /
• 1989

We consider the step stress life testing which has been developed in order to perform the life testing of the units whose normal life time is long within a reasonable amount of time. The models suggested for statistical analysis of the data obtained form the stress life testing are reviewed and a model which contains these models in some respect is suggested. The statistical inference based on the suggested model is done using maximum likelihood and weighted least square estimates. Finally we review the design of the simple step stress life testing and extend the result to the censoring case.

• The Korean Journal of Applied Statistics
• /
• v.31 no.1
• /
• pp.41-65
• /
• 2018

In Korea, as the mortality rate improves in a shorter period of time than in developed countries, it is important to consider the selection of the time series as well as the model selection in the mortality projection. Therefore, this study proposed a method using the multiple regression model in respect to the selection of the time series period. In addition, we investigate the problems that arise when various time series are used based on the Lee-Carter (LC) model, the kinds of LC model along with Lee-Miller (LM) and Booth-Maindonald-Smith (BMS), and the non-parametric model such as functional data model (FDM) and Coherent FDM, and examine differences in the age-specific mortality rate and life expectancy projection. Based on the analysis results, the age-specific mortality rate and predicted life expectancy of men and women are calculated for the year 2030 for each model. We also compare the mortality rate and life expectancy of the next generation provided by Korean Statistical Information Service (KOSIS).

• Communications for Statistical Applications and Methods
• /
• v.6 no.2
• /
• pp.423-432
• /
• 1999

Accelerated life testing of product is commonly used to reduced test time and costs. In this papers is considered when the product is a two component system with lifetimes following the bivariate exponential distribution of Sarkar(1987) using inverse power rule model. Also we derived the maximum likelihood estimators of parameters for asymptotic normality. We compare the mean square error of the proposed estimator for the life distribution under use conditions stree through Monte Carlo simulation.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 1999.05a
• /
• pp.57-61
• /
• 1999

Electrical stress makes insulating materials aged finally resulting in the dielectric failure. It becomes more and more important to recognize the degree of aging and the life time of the insulating materials since it is directly concerned with the reliability of the insulation system. In this paper, the life time of the Cross-linked Polyethylene(XLPE), the insulation layer in the 154kV-grade power cable, is expected and calculated using statistical and mathematical methods. The simulated results are compared with experimental ones and the life exponent of the material is obtained.

• Journal of Family Resource Management and Policy Review
• /
• v.20 no.1
• /
• pp.23-42
• /
• 2016

The purpose of this study was to explore a typology of leisure participation, investigate determinants of leisure participation types, and analyze differences in life satisfaction by the types of leisure participation of the elderly. The data source for this research was the 2014 Time Use Survey conducted by the Korea National Statistical office (KNSO). The statistical methods for the analysis were mean, standard deviation, ANOVA, Duncan test, cluster analysis, and logistic regression analysis. Leisure participation were classified into five types based on five categories; social activities, religious activities, media, sports, time-spending activity. The five types were named "general", "insufficient", "religious oriented", "media oriented", and sports oriented" type. Gender, health condition were identified as important determinants for the types. Life satisfaction was different according to leisure participation type of the elderly. Religious oriented type showed the highest score of life satisfaction and media oriented type showed the lowest.

• Communications for Statistical Applications and Methods
• /
• v.17 no.1
• /
• pp.89-98
• /
• 2010

In this paper, a two-stage group sampling plan based on the time truncated life test is proposed for the Weibull distribution. The design parameters such as the number of groups and the acceptance number in each stage are determined by satisfying the producer's and consumer's risks simultaneously when the group size and the test duration are specified. The acceptable reliability level is expressed by the ratio of the true mean life to the specified life. It was demonstrated from the comparison with single-stage group sampling plans that the proposed plan can reduce the average sample number or improve the operating characteristics.

• Korean Journal of Human Ecology
• /
• v.15 no.6
• /
• pp.985-997
• /
• 2006

In this study, we grasped the life time structure according to working woman's income using '2004 life time research' of Korea National Statistical Office. Concrete results are shown as follows. First, inspecting the difference of individual characteristic according to income, young women who have higher education level and larger house area had acquired more income. Second, in case of the difference of life time according to income, there was no difference of individual support time, while there was statistically significant difference of working hours, household affairs, leisure time and moving hours. Third, inspecting the individual time of working, household affairs, bringing up and leisure according to income, there was statistically significant difference by age, education level, sense of time oppression, and fatigue cognition. This individual difference was revealed more strongly in medium to low-ranked group.