• Title, Summary, Keyword: Test of heterogeneity

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Statistical methods for testing tumor heterogeneity (종양 이질성을 검정을 위한 통계적 방법론 연구)

  • Lee, Dong Neuck;Lim, Changwon
    • The Korean Journal of Applied Statistics
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    • v.32 no.3
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    • pp.331-348
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    • 2019
  • Understanding the tumor heterogeneity due to differences in the growth pattern of metastatic tumors and rate of change is important for understanding the sensitivity of tumor cells to drugs and finding appropriate therapies. It is often possible to test for differences in population means using t-test or ANOVA when the group of N samples is distinct. However, these statistical methods can not be used unless the groups are distinguished as the data covered in this paper. Statistical methods have been studied to test heterogeneity between samples. The minimum combination t-test method is one of them. In this paper, we propose a maximum combinatorial t-test method that takes into account combinations that bisect data at different ratios. Also we propose a method based on the idea that examining the heterogeneity of a sample is equivalent to testing whether the number of optimal clusters is one in the cluster analysis. We verified that the proposed methods, maximum combination t-test method and gap statistic, have better type-I error and power than the previously proposed method based on simulation study and obtained the results through real data analysis.

RELATIONSHIP BETWEEN VIRULENCE, METABOLIC ACID AND GENETIC HETEROGENEITY OF PORPHYROMONAS GINGIVALIS (Porphyromonas gingivalis의 독성, 대사산물 및 유전자이종성과의 관련성)

  • Kim, Kang-Ju;Chung, Chong-Pyoung
    • Journal of Periodontal and Implant Science
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    • v.23 no.1
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    • pp.1-15
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    • 1993
  • P. gingivalis has been implicated as a strong pathogen in periodontal disease and known to have three serotypes of P. gingivalis. The purpose of this study is to investigate on the relationship between virulence, metabolic acids and genetic heterogeneity of P. gingivalis. P. gingivalis W50 standard strain and five strains of P. gingivalis serotype b Korean isolates were used in this study. For in vitro virulence test, lyophilized whole cell P. gingivalis were suspended, and sonicated with ultrasonic dismembranometer. Sonicated samples were applied to cultured cells derived from periodontal ligament, and cell activity was assayed with growth and survival assay. The metabolic acids were also extracted, and determined by High Performance Liquid Chromatography. Pst I-digested bacterial genomic DNA was electrophoresed, and densitometric analysis was performed to study the genetic heterogeneity. All of the P. gingivalis serotype b produced butyric acid. In cell activity study, butyric acid inhibited the cell activity irrespective of its concentration. Densitometric analysis showed restriction fragment length polymorphism. These results suggested that there existed heterogeneity of the metabolic acids and the virulence of P. gingivalis and such heterogeneity might be related to genetic heterogeneity.

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수리지질학적 조건에 따른 지하수유동 및 오염물질이동 영향연구

  • 이진용;이강근
    • Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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    • pp.280-282
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    • 2002
  • In analysis of pumping test data, generally infinite domain has been assumed. However, in many cases, this assumption was not readily satisfied. Some boundaries conditions and natural heterogeneity of hydrogeologic properties would play critical roles on groundwater flow and contaminant transport. This study examined effects of some boundary conditions and heterogeneity on the groundwater flow and contaminant transport with basic numerical groundwater modeling, which provides implications for remediation of contaminated groundwater.

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Estimation of Genetic Parameters for Milk Production Traits Using a Random Regression Test-day Model in Holstein Cows in Korea

  • Kim, Byeong-Woo;Lee, Deukhwan;Jeon, Jin-Tae;Lee, Jung-Gyu
    • Asian-Australasian Journal of Animal Sciences
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    • v.22 no.7
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    • pp.923-930
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    • 2009
  • This study was conducted to compare three models: two random regression models with and without considering heterogeneity in the residual variances and a lactation model (LM) for evaluating the genetic ability of Holstein cows in Korea. Two datasets were prepared for this study. To apply the test-day random regression model, 94,390 test-day records were prepared from 15,263 cows. The second data set consisted of 14,704 lactation records covering milk production over 305 days. Raw milk yield and composition data were collected from 1998 to 2002 by the National Agricultural Cooperative Federation' dairy cattle improvement center by way of its milk testing program, which is nationally based. The pedigree information for this analysis was collected by the Korean Animal Improvement Association. The random regression models (RRMs) are single-trait animal models that consider each lactation record as an independent trait. Estimates of covariance were assumed to be different ones. In order to consider heterogeneity of residual variance in the analysis, test-days were classified into 29 classes. By considering heterogeneity of residual variance, variation for lactation performance in the early lactation classes was higher than during the middle classes and variance was lower in the late lactation classes than in the other two classes. This may be due to feeding management system and physiological properties of Holstein cows in Korea. Over classes e6 to e26 (covering 61 to 270 DIM), there was little change in residual variance, suggesting that a model with homogeneity of variance be used restricting the data to these days only. Estimates of heritability for milk yield ranged from 0.154 to 0.455, for which the estimates were variable depending on different lactation periods. Most of the heritabilities for milk yield using the RRM were higher than in the lactation model, and the estimate of genetic variance of milk yield was lower in the late lactation period than in the early or middle periods.

Effect of Aflatoxin on Feed Conversion Ratio in Broilers: A Meta-analysis

  • Suganthi, R. Umaya;Suresh, K.P.;Parvatham, R.
    • Asian-Australasian Journal of Animal Sciences
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    • v.24 no.12
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    • pp.1757-1762
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    • 2011
  • Aflatoxins are natural contaminants of poultry feeds and feed ingredients and cause liver damage, immunosuppression, reduction in performance and mortality in broilers. A number of studies have been carried out to study the effects of aflatoxin on feed conversion ratio in broilers. The results on feed conversion ratio of 10 research articles in broilers fed with aflatoxin from first day of age to six weeks of age were compiled and were subjected to meta-analysis. Chi-square test and $Tau^2$ (heterogeneity co-efficient) were applied to test for significance of heterogeneity of studies. To integrate results, fixed effect model by Inverse Variance method (IV method) was used when heterogeneity was insignificant and otherwise random effect model by DerSimonian and Laird Method (DL method) was used. The results of meta-analysis showed that the adverse effect of aflatoxin on feed conversion ratio at the end of first week was negligible, second week was medium and third to six weeks was very large.

A minimum combination t-test method for testing differences in population means based on a group of samples of size one (크기가 1인 표본들로 구성된 집단에 기반한 모평균의 차이를 검정하기 위한 최소 조합 t-검정 방법)

  • Heo, Miyoung;Lim, Changwon
    • 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.

The Impact of Environmental Characteristics on Electronic Commerce Performance

  • Cho, Se-Hyung
    • Proceedings of the Korea Society of Information Technology Applications Conference
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    • pp.357-360
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    • 2005
  • Domestic enterprises are surveyed and analyzed to find the empirical relationship between environmental characteristics and electronic commerce(EC) performance. Dynamism, hostility and heterogeneity are selected as environmental characteristics. EC performance is articulated as EC utilization, EC satisfaction and EC usefulness. Empirical test presents that dynamism has a statistically significant relationship with EC performance except EC usefulness, but hostility and heterogeneity have no statistically significant relationship with EC performance. The impact of industry type on environmental characteristics and EC performance is also tested.

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Anti-Diabetic Medications Do Not Influence Risk of Lung Cancer in Patients with Diabetes Mellitus: a Systematic Review and Meta-analysis

  • Nie, Shu-Ping;Chen, Hui;Zhuang, Mao-Qiang;Lu, Ming
    • Asian Pacific Journal of Cancer Prevention
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    • v.15 no.16
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    • pp.6863-6869
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    • 2014
  • Objectives: Several preclinical and observational studies have shown that anti-diabetic medications (ADMs) may modify the risk of lung cancer. We performed a systematic review and meta-analysis evaluating the effect of metformin, sulfonylureas (SUs), thiazolidinediones (TZDs), and insulin on the risk of lung cancer in patients with diabetes mellitus (DM). Materials and Methods: We conducted a systematic search of Pubmed and Web of Science, up to August 20, 2013. We also searched the Conference Proceedings Citation Index (CPCI) and China National Knowledge Infrastructure (CNKI) for abstracts from major meetings. Fixed or random effect pooled measures were selected based on heterogeneity among studies, which was evaluated using Q test and the I2 of Higgins and Thompson. Meta-regression was used to explore the sources of between-study heterogeneity. Publication bias was analyzed by Begg's funnel plot and Egger's regression test. Associations were assessed by odds ratios (ORs) with 95% confidence intervals (CIs). Results: A total of 15 studies (11 cohort, 4 case-control) were included in this meta-analysis. In observational studies no significant association between metformin (n=11 studies; adjusted OR=0.99, 95%CI: 0.87-1.12), SUs (n=5 studies; adjusted OR=0.98, 95%CI: 0.79-1.22), or TZDs (n=7 studies; adjusted OR=0.92, 95%CI: 0.75-1.13), insulin (n=6 studies; adjusted OR=1.13, 95%CI: 0.79-1.62) use and risk of developing lung cancer was noted. There was considerable inherent heterogeneity between studies not explained by study design, setting, or location. Conclusions: Meta-analysis of existing studies does not support a protective or harmful association between ADMs use and risk of lung cancer in patients with DM. There was considerable heterogeneity across studies, and future, well-designed, prospective studies would be required for better understanding of any association.

Epstein-Barr Virus and Gastric Cancer Risk: A Meta-analysis With Meta-regression of Case-control Studies

  • Bae, Jong-Myon;Kim, Eun Hee
    • Journal of Preventive Medicine and Public Health
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    • v.49 no.2
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    • pp.97-107
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    • 2016
  • Objectives: Research on how the risk of gastric cancer increases with Epstein-Barr virus (EBV) infection is lacking. In a systematic review that investigated studies published until September 2014, the authors did not calculate the summary odds ratio (SOR) due to heterogeneity across studies. Therefore, we include here additional studies published until October 2015 and conduct a meta-analysis with meta-regression that controls for the heterogeneity among studies. Methods: Using the studies selected in the previously published systematic review, we formulated lists of references, cited articles, and related articles provided by PubMed. From the lists, only case-control studies that detected EBV in tissue samples were selected. In order to control for the heterogeneity among studies, subgroup analysis and meta-regression were performed. Results: In the 33 case-control results with adjacent non-cancer tissue, the total number of test samples in the case and control groups was 5280 and 4962, respectively. In the 14 case-control results with normal tissue, the total number of test samples in case and control groups was 1393 and 945, respectively. Upon meta-regression, the type of control tissue was found to be a statistically significant variable with regard to heterogeneity. When the control tissue was normal tissue of healthy individuals, the SOR was 3.41 (95% CI, 1.78 to 6.51; I-squared, 65.5%). Conclusions: The results of the present study support the argument that EBV infection increases the risk of gastric cancer. In the future, age-matched and sex-matched case-control studies should be conducted.

The Examination of Direct and Indirect Transmission Processes of Intergenerational Marital Instability (결혼불안정성의 세대간의 직, 간접전이에 관한연구)

  • Peter Martin
    • Journal of Korean Home Management Association
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    • v.15 no.1
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    • pp.191-200
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    • 1997
  • The purpose of this research was to test a model of intergenerational transmission of marital instability. An important aspect of the present study was to test the direct and indiect intergenerational transmission processes of marital instability. This study revealed four very important findings. First the effects of parental divorce on children's marital instability were both direct and indirect through mate selection risk factors marital quality and marital commitment. Second premarital backgrounds such as socioeconomic status of parents and relative heterogeneity between spouse before marriage were important to explain one's marital relationship. Third the higher the barriers the higher the marital commitment. Fourth marital quality and marital commitment were important predictors of marital instability. Taken together this study supports the intergenerational transmission perspective that exposure to conflict marriage in one's own childhood would forecast lower marital sat sfaction higher conflict and higher marital instability in the marital relationship. The findings from this study also underline the importance of predisposing marital characteristics such as parental socioeconomic status and relative heterogeneity in explaining marital relationship.

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