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

• Communications for Statistical Applications and Methods
• /
• v.4 no.3
• /
• pp.775-785
• /
• 1997

Robustness rates for repeated measures pairwise multiple comparison procedures were investigated in a split plot design with one between- and one within-subjects factor using untrimmed and trimmed data. Five factors were manipulated in the study: distribution, sphericity, variance-covariance heteroscedasticity, total sample size, and sample size ratio. The Welsch test (W) and the Welsch test on trimmed data $(W_{RT})$ performed better than the other procedures, but had a liberal tendency. The trimmed difference score Bonferroni Procedure $(B_{DT})$ was a good choice in some conditions.

• Journal of the Korean Society of School Health
• /
• v.10 no.1
• /
• pp.51-63
• /
• 1997

Changes in disease patterns increase the importance of health-promoting lifestyles in a healthy society. Thus health education in elementary schools is very important because the knowledge of health and health habits in this period become a habitual part of life. The purpose of this study is to identify the performance in promoting healthy lifestyles of elementary school nurses. Such data helps to provide data to judge whether they are capable health educators or not. The subjects were 365 elementary school nurses selected by purposive sample. The data were collected by a self reporting questionnaire from August to October of 1996. The methods used in this study were the health-promoting lifestyle profile developed by Park In Sook (1995) and Licker's flour-point scale. A Cronbach's ${\alpha}$, percentage, mean, standard deviation, ANOVA, Pearson's correlation coffcient and stepwise multiple regression in the SAS package were used to analyze the data. The results of this study were as follows: 1. 37.7% of the sample were aged between 30 and 39 and 33.7% were between 40 and 49. 44.9% of the sample had attended college. 87.7% of the sample were married. 42.5% of the sample were people with a career of 11~20 years, and 26.0% of it had 21 years or more of working experience as an elementary school nurses. 2. The average scores of the family function and the social support were 2.97 and 2.98 respectively. 3. 86.5% of the sample were satisfied with their job. 4. 85.8% of the sample answered that they were healthy and 14.2% answered that they were unhealthy. The average scores of the internal health locus of control and self-esteem were 3.35 and 3.15 respectively. 5. The average score of performance in health-promoting lifestyle variables was 3.16; the average scores for harmonious relationships, regular diet professional health maintenance, sanitary life, self-control, emotional support, diet, rest and sleep, exercise and activity. self-achievement, and diet control were 3.47, 3.30, 2.52. 3.60, 2.92, 3.18, 3.14, 3.11, 2.96, 3.26 and 3.12. The variable with the highest degree of correlation was a sanitary life, whereas the one with the lowest degree was professional health maintenance. 6. A significant difference was found in self-esteem according to age. There was a significant difference in the average score of internal health locus of control according to age and career. 7. There were significant differences in the health-promoting lifestyle performance depending on age, career and monthly household income. The longer the career, the higher the health-promoting lifestyle performance. 8. A weak positive correlation was found between self-esteem and health-promoting lifestyles performance(r=0.417, p<0.001) Also, a weak positive correlation was found between the internal health locus of control and health-promoting lifestyles performance (r=0.386, p<0.001). 9. Heath-promoting lifestyle performance showed significant correlations with family function, social support and job satisfaction. 10. Stepwise multiple regression analysis revealed that the most powerful predictor was the variance of family function. Social support, age, self-esteem, internal health locus of control, perceived heath status and job satisfaction accounted for 55.9% of the variance in heath-promoting lifestyle performance.

• Clinical and Experimental Reproductive Medicine
• /
• v.49 no.3
• /
• pp.196-201
• /
• 2022

Objective: This prospective consecutive study investigated the variation in sperm DNA fragmentation (SDF) in multiple semen samples from patients with cancer. Methods: Eighty-one patients with various cancers underwent multiple semen collections on 3 consecutive days for sperm cryopreservation prior to cancer treatment. A commercial Halosperm kit was used to measure SDF. Within- and between-subject coefficients of variation were estimated via random-effects analysis of variance to assess the consistency of semen parameters and SDF. Intraclass correlation coefficients (ICCs) were calculated to assess the magnitude of the between-subject component of variance relative to the total variance. Results: The volume of semen in the day-2 and day-3 samples was significantly lower compared with the day-1 sample. Most parameters showed high ICC values, suggesting that within-subject fluctuations were small relative to the between-subject variability. The highest ICC values were identified for the SDF (ICC, 0.68; 95% confidence interval [CI], 0.45-0.84) and semen volume (ICC, 0.67; 95% CI, 0.45-0.84). Conclusion: Our findings showed that repeated ejaculates from patients with cancer had stable SDF levels.

• Journal of the Korean Operations Research and Management Science Society
• /
• v.39 no.4
• /
• pp.137-152
• /
• 2014

In this paper, I suggest several techniques to estimate covariance matrix and compare the performance of the global minimum variance portfolio (GMVP) in terms of out of sample mean standard deviation and return. As a result, the return differences among the GMVPs are insignificant. The mean standard deviation of the GMVP using historical covariance is sensitive to the estimation window and the number of assets in the portfolio. Among the model covariance, the GMVP using constant systematic risk ratio model or using short sale restriction shows the best performance. The performance difference between the GMVPs using historical covariance and model covariance becomes insignificant as the historical covariance is estimated with longer estimation window. Lastly, the implied volatilities from ELW prices do not lead to superior performance to the historical variance.

• Genomics & Informatics
• /
• v.20 no.1
• /
• pp.9.1-9.6
• /
• 2022

Mendelian randomization (MR) uses genetic variation as a natural experiment to investigate the causal effects of modifiable risk factors (exposures) on outcomes. Two-sample Mendelian randomization (2SMR) is widely used to measure causal effects between exposures and outcomes via genome-wide association studies. 2SMR can increase statistical power by utilizing summary statistics from large consortia such as the UK Biobank. However, the first-order term approximation of standard error is commonly used when applying 2SMR. This approximation can underestimate the variance of causal effects in MR, which can lead to an increased false-positive rate. An alternative is to use the second-order approximation of the standard error, which can considerably correct for the deviation of the first-order approximation. In this study, we simulated MR to show the degree to which the first-order approximation underestimates the variance. We show that depending on the specific situation, the first-order approximation can underestimate the variance almost by half when compared to the true variance, whereas the second-order approximation is robust and accurate.

• The Korean Journal of Financial Management
• /
• v.21 no.1
• /
• pp.231-253
• /
• 2004

We examine hedge strategies that use Won-dollar futures to hedge the price risk of the Won-dollar exchange rate. We employ the naive hedge model, minimum variance hedge model and bivariate ECT-ARCH(1) model as hedge instruments, and analyze their hedge performances. The sample period covers from January 2, 2001 to December 31, 2002 with sub-samples such as daily, weekly, bi-weekly prices of the Won-dollar futures and cash. The important findings may be summarized as follows. First, there is no significant difference in hedge ratio between the risk minimum variance model and bivariate ECT-ARCH(1) model that controls for the cointegration relationship of the Won-dollar futures and cash. Second, hedge performance of the naive model and minimum variance model with constant hedge ratios is not far behind that of bivariate ECT-ARCH(1) model with time-varying hedge ratios. This results imply that investors are encouraged to use the minimum variance hedge model to hedge Won-dollar exchange rate with Won-dollar futures. Third, hedge performance and effectiveness of each model is also analyzed with respect to hedge period appear to be greater over long than over the short period. This evidence supports the hypothesis that futures prices would have more time to respond to the greater cash price changes over the longer holding period, leading to an improved hedge performance.

• Asian Journal of Business Environment
• /
• v.4 no.3
• /
• pp.13-18
• /
• 2014

Purpose - This study examines students' perspectives (stream-wise) of parameters affecting education quality in an affiliated undergraduate engineering institution in NCR, Haryana. Research design, data, and methodology - This study involves descriptive research and data collection using a structured questionnaire based on the Likert scale. The sample comprises 500 student respondents. For data analysis, an f-test was performed using high quality SPSS software. Results - For "Selection" and "Personality Development & Industry Exposure," the analysis of variance revealed a statistical difference between the mean values of the groups. Whereas, for "Academic Excellence," "Infrastructure," "Placements," and "Management & Administration," the analysis of variance revealed no statistical difference between the mean values of the groups. Conclusions - Students' perceptions about the "Selection" and "Personality Development & Industry Exposure" change according to the various specializations they opt for in their undergraduate engineering education in Haryana. Whereas, for "Academic Excellence," "Infrastructure," "Placements," and "Management & Administration," the perceptions of the students do not vary because of the different specializations they have opted for in their undergraduate engineering education.

• Clinics in Shoulder and Elbow
• /
• v.25 no.3
• /
• pp.173-181
• /
• 2022

Background: Healing of the tendon itself is not always related to successful clinical outcomes after rotator cuff repair. It was hypothesized that certain radiologic factors affecting clinical outcomes could exist in case of the retear after arthroscopic rotator cuff repair (ARCR) and the radiologic factors could help predict clinical process. The purpose of this study was to identify the radiologic factors associated with clinical outcomes of the retear after ARCR. Methods: Between January 2012 and December 2019, among patients with sufficient footprint coverage for ARCR, 96 patients with Sugaya classification 4 or higher retear on follow-up magnetic resonance imaging were included. The association between clinical outcomes such as American Shoulder and Elbow Surgeons (ASES) score, Constant score and range of motion and radiologic variables such as initial tear dimension, retear dimension, variance of tear dimension, critical shoulder angle, acromial index, and acromiohumeral distance was analyzed. Results: Preoperatively, the ASES and Constant scores were 59.81±17.02 and 64.30±15.27, respectively. And at the last follow-up, they improved to 81.56±16.29 and 78.62±14.16, respectively (p<0.01 and p<0.01). In multiple linear regression analysis, the variance of the mediolateral dimension of tear had statistically significant association with the ASES and Constant scores (p<0.01 and p=0.01). Conclusions: In patients with the retear after ARCR, the variance in the mediolateral dimension of tear had significantly negative association with the clinical outcomes. This could be considered to be reference as relative criteria and needed more sample and mechanical study.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.26 no.9
• /
• pp.828-836
• /
• 2015

In this paper, the assessment technique for track accuracy in the phased array radar is proposed. It is assumed that ${\alpha}-{\beta}$ tracking filter to track the target is established in the phased array radar. In order to assess the track accuracy strictly, we should use the real target position data acquired from the special instrument, ACMI(Air Combat Maneuvering Instrument) pod or DGPS(Differential Global Positioning System). However, this method leads to increase the experiment cost and test time. We derive the relationship between the residuals of tracking filter and the standard deviations of range and angle tracking errors which are assigned as track assessment index. The theory of sample variance is introduced in this assessment because track accuracy has to be calculated with many residual samples.