• Journal of the Korean Data and Information Science Society
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• v.9 no.2
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• pp.289-298
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• 1998

We investigate the distribution of likelihood ratio test(LRT) of null hypothesis a sample is from single gamma with unknown shape and scale against the alternative hypothesis a sample is from a mixture of two gammas, each with unknown scale and unknown (but equal) scale. To obtain stable maximum likelihood estimates(MLE) of a mixture of two gamma distributions, the EM(Dempster, Laird, and Robin(1977))and Modified Newton(Jensen and Johansen(1991)) algorithms were implemented. Based on EM, we made a simple structure likelihood equation for each parameter and could obtain stable solution by Modified Newton Algorithms. Simulation study was conducted to investigate the distribution of LRT for sample size n = 25, 50, 75, 100, 50, 200, 300, 400, 500 with 2500 replications. To determine the small sample distribution of LRT, I considered the model of a gamma distribution with shape parameter equal to 1 + f(n) and scale parameter equal to 2. The simulation results indicate that the null distribution is essentially invariant to the value of the shape parameter. Modeling of the null distribution indicates that it is well approximated by a gamma distribution with shape parameter equal to the quantity $0.927+1.18/\sqrt{n}$ and scale parameter equal to 2.16.

• Journal of the Korean Data and Information Science Society
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• v.21 no.2
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• pp.291-296
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• 2010

In this paper, we consider a versatile test based on percentile tests. The versatile test may be useful when the underlying distributions are unknown or quite different types. We consider two kinds of combining functions for the percentile statistics, the quadratic and summing forms and obtain the limiting distributions under the null hypothesis. Then we illustrate our procedure with an example. Finally we discuss some interesting features of the test as concluding remarks.

• Journal of the Korean Statistical Society
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• v.1 no.1
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• pp.11-17
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• 1973

A class of sequential binomial tests and a sequential rank test can be applied for testing two treatments when subjects are paired in many-to-one ratio. The efficiency of each test is examined in terms of the average sample number. The binomial tests are much easier and more convenient to apply than the rank test not as efficient. Within the class of binomial test, the median test appears to be the most efficient is general.

• Interdisciplinary Bio Central
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• v.2 no.2
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• pp.4.1-4.6
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• 2010

The most common type of microarray experiment has a simple design using microarray data obtained from two different groups or conditions. A typical method to identify differentially expressed genes (DEGs) between two conditions is the conventional Student's t-test. The t-test is based on the simple estimation of the population variance for a gene using the sample variance of its expression levels. Although empirical Bayes approach improves on the t-statistic by not giving a high rank to genes only because they have a small sample variance, the basic assumption for this is same as the ordinary t-test which is the equality of variances across experimental groups. The t-test and empirical Bayes approach suffer from low statistical power because of the assumption of normal and unimodal distributions for the microarray data analysis. We propose a method to address these problems that is robust to outliers or skewed data, while maintaining the advantages of the classical t-test or modified t-statistics. The resulting data transformation to fit the normality assumption increases the statistical power for identifying DEGs using these statistics.

• Journal of Sericultural and Entomological Science
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• v.13 no.1
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• pp.69-72
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• 1971

1. To study proper sample size in boiling-of test, we extracted samples in size of 200, 100, 50, 20, and 10 grams and tested them. In the result of this test we couldn't find a statistical significance among them, but it is seemed that the proper sample size is 100 gram to think about the errors of measurement and treatment when the sample size is either too little or too much in ordinary test. 2. We tested boil-of result by twisted sample skein (sizing skein) and untwisted sample. In this test to use sodium carbonate (Na$_2$CO$_3$) having powerful sericin dissolving power as a scouring agent, boil-off percents made no statistical significance between two kinds of sample skein. And to use marseilles soap having less powerful sericin dissolving power as a scouring agent, boil-off percents made a difference between twisted and untwisted sample skein. 3. We compared five kinds of scouring agent, for example sodium carbonate, monogen, synthetic detergent (HiTi), marseilles soap A (made in Japan) and marseilles soap B (made in Korea). Among them synthetic detergent and marseilles soap B showed no statistical significance compared with marseilles soap A which we used in ordinary boil-off test. So synthetic detergent and marseilles soap B can be substituted for marseilles soap A. 4. Generally the higher pH value of boil of solution, tile more sericin dissolution, showed and vice versa.

• The Korean Journal of Applied Statistics
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• v.30 no.2
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• pp.301-309
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• 2017

It is often possible to test for differences in population means when two or more samples are extracted from each N population. However, it is not possible to test for the mean difference if one sample is extracted from each population since a sample mean does not exist. But, by dividing a group of samples extracted one by one into two groups and generating a sample mean, we can identify a heterogeneity that may exist within the group by comparing the differences of the groups' mean. Therefore, we propose a minimum combination t-test method that can test the mean difference by the number of combinations that can be divided into two groups. In this paper, we proposed a method to test differences between means to check heterogeneity in a group of extracted samples. We verified the performance of the method by simulation study and obtained the results through real data analysis.

• Korean Journal of Clinical Laboratory Science
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• v.44 no.3
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• pp.124-127
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• 2012

Syphilis is an infectious and sexually transmitted chronic disease caused by Treponema pallidum. On the basis of clinical findings, the disease has been divided into a series of overlapping stages, which are used to help guide treatment and follow-up. Persons who have syphilis might seek treatment for signs or symptoms of primary infection, secondary infection and tertiary infection. Latent infections are detected by serologic testing. A presumptive diagnosis of syphilis is possible with the use of two types of serologic tests: nontreponemal tests and treponemal tests assay. The use of only one type of serologic test is insufficient for diagnosis, because each type of test has limitations, including the possibility of false-positive test results in persons without syphilis. KFDA published Koreans guideline of Sexually transmitted infections in 2011. Two hundred samples were tested by RPR card test and Mediace RPR test with simultaneously. The agreement between RPR card test and Mediace RPR test was 95%, the discrepant samples was 5%. The characteristics of 10 discrepant samples was RPR card Positive and Mediace RPR negative nine samples, RPR card negative and Mediace RPR positive one sample. The nine samples were confirmed as FTA-ABS by KFDA guideline of syphilis test algorism, all IgM test was Negative, all IgG test was reactive. So, these cases were past or latent syphilis. The one sample was false-positive reaction.

• Journal of the Korean Statistical Society
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• v.30 no.4
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• pp.679-691
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• 2001

Two truncated sequential tests are developed for the two-sample scale problem based on the usual Wilcoxon rank-sum statistic for two different dispersion indices - absolute median deviations, when the medians of the two populations X and Y are equal or known and sums of squared mean deviations, when the medians are either unknown or unequal. The first test is briefly called SWAMD test and the second SWSMD test. For the SWAMD test, the percentile points for both the one-sided and two-sided alternatives, (equation omitted) have been found by Wiener approximation and their values computed for a range of values of a and N; analytical expression for the power function has been derived through Wiener process and its performance studied for various sequential designs for exponential distribution. This test has been illustrated by a numerical example. All the results of the SWAMD test, being directly applicable to the SWSMD test, are not dealt with separately Both the tests are compared and their suitable applications indicated.

• Journal of Korean Society for Quality Management
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• v.34 no.1
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• pp.20-26
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• 2006

In the fields of mechanical reliability application, "zero" or "zero or one" failure tests are most commonly used for demonstrating reliability of a product since they reduce test duration and/or sample size compared to other test methods that guarantees the same reliability of a product with a given confidence level or consumer's risk. The test duration of the "zero or one" failure test is longer than that of "zero" failure test but it has advantage of smaller producer's risk. In this paper a two-stage test is developed that compromises the "zero" and "zero or one" failure tests. The properties of the proposed two-stage test are investigated and the three test methods are compared using a numerical example.

• Journal of radiological science and technology
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• v.35 no.1
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• pp.35-44
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• 2012

The goal of this study is to awaken about risk occurred by CT examination. For radio-technologists working at 'S medical center' located in Seoul, we investigated a recognition about dose and risk CT and normal X-ray examination according by working experience in hospital, experience about CT examination and radiation source. For subjects of investigation, radio-technologists working at 'S medical center' located in Seoul helped us. We collected 131 questionnaires for a test of hypothesis. Cronbach @ coefficients of questionnaires were 0.825988 and 0.767161 and a rejection rate of p-value was below 0.05. SAS 9.1(SAS Institute Inc., Cary, NC, USA.) statistic package was used for hypothesis test. We used Mann-Whitney test, Kruskai-Wallis test, Two sample T-test, Two sample T-test with Bonferroni's Correction and One-way ANOVA methods. P-values of hypothesis about dose of CT and normal X-ray examination were 0.2291 ~ 0.9663. p-values of hypothesis about risk were 0.1924 ~ 1.0000. All of hypothesis is over rejection rate(<0.05). This study shows that radio-technologists of S medical center recognized that CT has higher dose and risk than general X-ray examination.