• International Journal of Reliability and Applications
• /
• v.1 no.1
• /
• pp.39-47
• /
• 2000

In a resent paper, Na and Kim(2000) develop a family of test statistics for testing whether or not the mean residual life changes its trend based on complete data and show that the new tests perform better than previously known tests. In this paper, we extend their tests to the randomly censored data. The asymptotic normality of the test statistics is established. Monte Carlo simulations are conducted to compare our tests with a previously known test by the power of tests.

• Journal of the Korean Data and Information Science Society
• /
• v.14 no.3
• /
• pp.561-570
• /
• 2003

We propose a nonparametric test procedure for checking the proportionality assumption between hazard functions using a functional equation. Because of the involvement of censoring distribution function, we consider the large sample case only and obtain the asymptotic normality of the proposeed test statistic. Then we discuss the rationale of the use of the functional equation, give some examples and compare the performances with Andersen's procedure by computing powers through simulations.

• Proceedings of the Korean Reliability Society Conference
• /
• 2000.11a
• /
• pp.365-371
• /
• 2000

The problem of trend change in the failure rate is great interest in the reliability and survival analysis. In this paper we develop a test statistic for testing whether or not the failure rate changes its trend using random censored data. The asymptotic normality of the test statistic is established. We discuss the efficiency values of loss due to censoring.

• Journal of the Korean Society for Aviation and Aeronautics
• /
• v.28 no.2
• /
• pp.53-62
• /
• 2020

This study is to evaluate the accuracy of the meteorological information provided for the aircraft operating at low altitude. At first, it is necessary to identify crucial elements of weather information closely related to flight safety during low altitude flights. The study conducted a survey of pilots of low altitude aircraft, divided into pre-flight and in-flight phases, and reached an opinion that wind direction, wind speed, cloud coverage and ceiling and visibility are important items. Related to these items, we compared and calculated the accuracy of TAFs and METARs from Taean Airfield, Seosan Airport and Gunsan Airport because of their high number of domestic low-altitude flights. Accuracy analysis evaluated the accuracy of two numerical variables, Mean Absolute Error(MAE) and Root Mean Square Error(RMSE), and the cloud coverage which is categorical variable was calculated and compared by accuracy. For numeric variables, one-way ANOVA, which is a parameter-test, was approached to identify differences between actual forecast values and observations based on absolute errors for each item derived from the results of MAE and RMSE accuracy analyses. To determine the satisfaction of both normality assumptions and equivalence variability assumptions, the Shapiro-Wilk test was performed to verify that they do not have a normality distribution for numerical variables, and for the non-parametric test, Kruscal-Wallis test was conducted to determine whether or not they are satisfied.

• Journal of Korean Institute of Industrial Engineers
• /
• v.10 no.2
• /
• pp.51-65
• /
• 1984

A process quality control system is designed which incorporates run tests, normality test, process capability studies, etc., into control chart scheme, and a software package for microcomputers is developed. The system is interactive and has data base management capabilities. All programs are written in BASIC language.

• Journal of Korean Medicine Rehabilitation
• /
• v.31 no.4
• /
• pp.157-166
• /
• 2021

Objectives This study is designed to evaluate the safety of Bojungikgi-tang soft extract in healthy male volunteers. Methods 12 healthy male volunteers were recruited and this study was carried out by a single center. Laboratory test results, vital signs of the volunteers were collected to evaluate safety. According to registration order, the 12 subjects were allocated by serial number. To evaluate safety, blood samples were taken and vital signs were checked 4 times - screening, pre administration, post administration and follow up-during the whole trial. The difference between pre (before medication [0 hr]) and post-administration (after medication [48 hr]) variables was summarized as mean±standard deviation. The normality test was performed using the Kolmogorov-Smirnov test and Shapiro-Wilk test. When the normality is satisfied, the paired t-test is applied. Otherwise, the non-parametric method, Wilcoxon signed rank test is applied. The significance level was p<0.05. The incidence of all adverse effects are shown in percentage. Results In the case of red blood cell, hemoglobin, hematocrit, lymphocytes, neutrophils, protein, γ-glutamyl transpeptidase values, the normality test result of the variable for the difference value before and after the dosing has a significance level <0.05. But most of values did not deviate from the normal range, and the deviation from the normal range could not be regarded as the significance associated with this clinical trial. And adverse event wasn't observed associated with the clinical trial drug. Conclusions Bojungikgi-tang soft extract were considered to be safe for healthy male volunteers.

• Communications for Statistical Applications and Methods
• /
• v.3 no.3
• /
• pp.25-30
• /
• 1996

In discriminant analysis the procedures commonly used to estimate the dimensionality involve testing a sequence of dimensionality hypotheses. There is a problem with the size of the test since dimensionality hypotheses are tested sequentially and thus they are actually conditional tests. The focus of this paper is to investigate in asymptotic sense what happens to the sequential testing procedure if the assumption of normality does not hold.

• International Journal of Reliability and Applications
• /
• v.9 no.1
• /
• pp.71-78
• /
• 2008

Based on the goodness of fit approach, a new test is presented for testing exponentiality versus exponential better (worse) than used (EBU (EWU)) class of life distributions. The new test is much simpler to compute, asymptotically normal, enjoys good power and performs better than previous tests in terms of power and Pitman asymptotic efficiencies for several alternatives.

• Communications for Statistical Applications and Methods
• /
• v.23 no.6
• /
• pp.563-574
• /
• 2016

In this study, we propose several simultaneous tests to detect the difference between means and variances for the two-sample problem when the underlying distribution is normal. For this, we apply the likelihood ratio principle and propose a likelihood ratio test. We then consider a union-intersection test after identifying the likelihood statistic, a product of two individual likelihood statistics, to test the individual sub-null hypotheses. By noting that the union-intersection test can be considered a simultaneous test with combination function, also we propose simultaneous tests with combination functions to combine individual tests for each sub-null hypothesis. We apply the permutation principle to obtain the null distributions. We then provide an example to illustrate our proposed procedure and compare the efficiency among the proposed tests through a simulation study. We discuss some interesting features related to the simultaneous test as concluding remarks. Finally we show the expression of the likelihood ratio statistic with a product of two individual likelihood ratio statistics.

• Communications for Statistical Applications and Methods
• /
• v.9 no.2
• /
• pp.533-542
• /
• 2002

In this paper, a covariate adjusted logrank test is considered for censored paired data under the Cox proportional hazard model. The proposed score test resembles the adjusted logrank test of Tsiatis, Rosner and Tritchler (1985), which is derived from the partial likelihood. The dependence structure for paired data is accommodated into the test statistic by using' sum of square type' variance estimators. Several weight functions are also considered, which produce a class of covariate adjusted weighted logrank tests. Asymptotic normality of the proposed test is established and simulation studies with moderate sample size show the proposed test works well, particularly when there are dependence structure between treatment and covariates.