• Genomics & Informatics
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• v.7 no.3
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• pp.148-151
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• 2009

Generally, larger sample size leads to a greater statistical power to detect a significant difference. We may increase the sample size for both case and control in order to obtain greater power. However, it is often the case that increasing sample size for case is not feasible for a variety of reasons. In order to look at change in power as the ratio of control to case varies (1:1 to 4:1), we conduct association tests with simulated data generated by PLINK. The simulated data consist of 50 disease SNPs and 300 non-disease SNPs and we compute powers for disease SNPs. Genetic Power Calculator was used for computing powers with varying the ratio of control to case (1:1, 2:1, 3:1, 4:1). In this study, we show that gains in statistical power resulting from increasing the ratio of control to case are substantial for the simulated data. Similar results might be expected for real data.

• Communications for Statistical Applications and Methods
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• v.16 no.4
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• pp.713-722
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• 2009

The estimation of odds ratio and corresponding confidence intervals for case-control data have been done by traditional generalized linear models which assumed that the logarithm of odds ratio is linearly related to risk factors. We adapt a lower-dimensional approximation of Gu and Kim (2002) to provide a faster computation in nonparametric method for the estimation of odds ratio by allowing flexibility of the estimating function and its Bayesian confidence interval under the Bayes model for the lower-dimensional approximations. Simulation studies showed that taking larger samples with the lower-dimensional approximations help to improve the smoothing spline estimates of odds ratio in this settings. The proposed method can be used to analyze case-control data in medical studies.

• Journal of Korean Medicine for Obesity Research
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• v.2 no.1
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• pp.25-36
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• 2002

Objective: The purposes of this study are to know the relations of abdominal obesity and ischemic stroke and to know what index could represent the abdominal obesity appropriately. Methods. We have done case-control study and recruited 97 ischemic stroke patients and 117 controls. Case is matched by control by individual matching. All participants had questionnaire, interview and then were examined waist-hip ratio, waist circumference and body mass index. Results : WC, WHR and Hypertension history had differences in two groups, case and control groups. But BMI and other factors weren't significant. According to Quartile of Waist Circumference, the two groups had the differences in hypertension history, diabetes history, smoking status, WHR, BMI, and weight and in the Quartile of Waist-Hip Ratio Quartile, past history of hypertension and diabetes, WC, BMI and weight had the significances. Sex, Age Adjusted and Multivariate Odds Ratio (95% Confidence Interval) of WC Quartile are 2.083, 1.628, 4.491 and 4.418, 4.964, 12.306, and in WHR, the Ors are 2.252, 5.743, 15.776 and 2.632, 8.918, 23.596. Conclusions: We knew from these results that abdominal obesity is very important risk factor of ischemic stroke and WHR more than WC is a good indicator of abdominal obesity, so we should reduce the WHR to prevent of ischemic stroke.

• Genomics & Informatics
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• v.10 no.2
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• pp.117-122
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• 2012

A sample size with sufficient statistical power is critical to the success of genetic association studies to detect causal genes of human complex diseases. Genome-wide association studies require much larger sample sizes to achieve an adequate statistical power. We estimated the statistical power with increasing numbers of markers analyzed and compared the sample sizes that were required in case-control studies and case-parent studies. We computed the effective sample size and statistical power using Genetic Power Calculator. An analysis using a larger number of markers requires a larger sample size. Testing a single-nucleotide polymorphism (SNP) marker requires 248 cases, while testing 500,000 SNPs and 1 million markers requires 1,206 cases and 1,255 cases, respectively, under the assumption of an odds ratio of 2, 5% disease prevalence, 5% minor allele frequency, complete linkage disequilibrium (LD), 1:1 case/control ratio, and a 5% error rate in an allelic test. Under a dominant model, a smaller sample size is required to achieve 80% power than other genetic models. We found that a much lower sample size was required with a strong effect size, common SNP, and increased LD. In addition, studying a common disease in a case-control study of a 1:4 case-control ratio is one way to achieve higher statistical power. We also found that case-parent studies require more samples than case-control studies. Although we have not covered all plausible cases in study design, the estimates of sample size and statistical power computed under various assumptions in this study may be useful to determine the sample size in designing a population-based genetic association study.

• Journal of Environmental Health Sciences
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• v.32 no.6
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• pp.578-584
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• 2006

This research was conducted to estimate the effect of C/N ratio control on composting of TNT (2,4,6 trinitrotoluene)-contaminated soil. Glucose or acetone was selected to control C/N ratio of the contaminated soil. The C/N ratios of the controlled experiment and no controlled one were 26.0 and 6.6, respectively. During 45days, the degradation efficiency (96.0 or 91.8%) of acetone or glucose C/N ratio controlled soil was higher than that (78.4%) of no C/N ratio controlled case. The first order degradation rate constant of glucose or acetone C/N ratio control was 0.0641 or 0.0820/day. This constant was over twice 0.0356/day of no C/N ratio control. The C/N ratio control with glucose or acetone also showed a rather high $CO_2$ evolution than that without C/N ratio control. It was proven that C/N ratio control for composting of TNT-contaminated soil improved the treatment efficiency.

• Proceedings of the KSME Conference
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• 2002.08a
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• pp.427-430
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• 2002

The present parer outlines the system identification and vibration control performance of air traffic control tower of Yangyang international airport with tuned mass damper(TMD). From the free vibration test, natural frequency, damping ratio and mode shape of tower are obtained and these values are compared with the values from numerical analysis. In the vibration control test to evaluate the vibration control performance, equivalent damping ratio increased by tuned mass damper are obtained in case the TMD is operated as passive mode. Damping ratio of tower evaluated from free vibration test is about $1.0{\%}$. It is very low value than damping ratio recommended in general code. Damping ratio of passive mode is about $5{\%}$. These equivalent damping ratio increased by TMD is enough to enhance the serviceability of tower structure under wind load.

• 한국디지털정책학회:학술대회논문집
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• 2006.12a
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• pp.327-336
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• 2006

The odds ratio is used for assessing the disease-exposure association, because epidemiological data for case-control of cohort studies are often summarized into 2 ${\times}$ 2 tables. In this paper we define the odds ratio function(ORF) that extends odds ratio used on discrete survival event data to continuous survival time data and propose estimation procedures with censored data. The first one is a nonparametric estimator based on the Nelson-Aalen estimator of comulative hazard function, and the others are obtained using the concept of empirical odds ratio. Asymptotic properties such as consistency and weak convergence results are also provided. The ORF provides a simple interpretation and is comparable to survival function or comulative hazard function in comparing two groups. The mean square errors are investigated via Monte Carlo simulation. The result are finally illustrated using the Melanoma data.

• Proceedings of the Korea Concrete Institute Conference
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• 1995.04a
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• pp.130-135
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• 1995

We can consider that the study on early evaluation of strength of concrete is useful to raise safety of building and utility of quality control of concrete is useful to raise safety of building and utility of quality control of concrete. In this paper, was proposed to method early to predict strength of concrete with key parameters, such as Water/Cement(W/C) ratio and Sand / Aggregate(S/A) ratio. Through a series of experiment, the obtained results are summarized as follow. $\circled1$ The ratio of resistance was decteased as the increase of W/C ratio. $\circled2$ The maximum value for the ratio of resistance and compressive strength was presented in the case of 40% S/A ratio. $\circled3$ The relationship. of the ratio of resistance and compressive strength on 28days according to the change of W/C and S/A ratio is to be: $F_{28}=-0.00104R^2 + 2.263R - 935.5$ (W/C Ratio) $F_{28} = 0.007R^2 - 10.693R - 4269.1$ (S/A Ratio)

• Journal of Korean Association for Spatial Structures
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• v.19 no.3
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• pp.93-100
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• 2019

In this study, the retractable-roof spatial structure was chosen as the analytical model and a tuned mass damper (TMD) was installed in the analytical model in order to control the seismic response. The analysis model is mainly consisted of runway trusses (RT) and transverse trusses (TT), and the displacement response was analyzed by installing TMD on those trusses. The mass of the single TMD which is installed in the analytical model was set to 1% of the total structure mass and the total TMD mass ratio was set to be 8% or 6%. In addition, the mass of a single TMD was varied depending on the number of installations. As a result of analyzing the optimal number of installations of TMD, the displacement response was reduced in all cases compared to the case without TMD. Above all, the case with 8 TMDs was the most effective in reducing he displacement response. However, in this case, as the load on the upper structure of the retractable-roof spatial structure increases, the total mass ratio of TMD was maintained and the number of TMDs was increased to reduce the mass ratio of one TMD.

• The Journal of Internal Korean Medicine
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• v.22 no.3
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• pp.423-430
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• 2001

Objects: The purpose of this case-control study was done to examine the relationship between stroke prevalence and the anthropometric indices(body mass index(BMI), modified Broca's method(Broca's index), waist circumference(WC), waist-hip ratio(WHR)), dyslipidemia, past medical history(heart disease, hypertension, diabetes mellitus(DM)), life-style factors(smoking, drinking) in Korean adults. Methods : The study group consisted of neurologically confirmed 116 stroke patients as the case group and 116 non-stroke patients as control group. Obesity were defined as $BMI{\geq}25kg/m^2,\;Broca's\;index{\geq}30%$, WC >94cm in male and WC >80cm in female, $WHR{\geq}0.9$ in male and $WHR{\geq}0.8$ in female. Oyslipidemia were defined as total $cholesterol{\geq}200mg/dl,\;triglyceride{\geq}200mg/dl,\;HDL-cholesterol {\leq}35mg/dl,\;LDL-cholesterol{\geq}160mg/dl$. Information on life-style factors and past medical history was obtained from personal interview. The analysis of the data was done by means of chi-square test(Pearson's chi-square test, Fisher's exact test) and student t-test. Results: The results were as follow. In the study group: Hypertension had a 4:05 odds ratio, Broca's $index{\geq}30%$ had a 1.98 odds ratio, WC >94cm in male had a 2.17 odds ratio, WC >80cm in female had a 2.80 odds ratio, $WHR{\geq}0.9$ in male had a 4.66 odds ratio, $WHR{\geq}0.8$ in female had a 5.35 odds ratio, but heart disease, DM, life-style factors, serum lipid and 8MI had no direct relationship with odds ratio(nonsignificant). By student t-test, risk factors for stroke were found to be total cholesterol(p=0,025), LDL-cholesterol(p=0.013), WC(p=0.000) and WHR(p=0.000). Conclusions: This study suggests that people should be advised to control hyperlitension, hyperlipidemia and obesity since these carry a risk of stroke.