• Korean Journal of Oriental Medicine
• /
• v.14 no.2
• /
• pp.87-91
• /
• 2008

Background and Purpose: The purpose of this study was investigate statistical validities of previously reported articles that used various statistical techniques such as t-test and analysis of variance. Methods: To analyze the statistical procedures, 66 original articles using those statistical methods were selected from "Korean Journal of Oriental Medicine(KJOM)" published from 1995 to 2007. Results: Twenty-one articles(32%) did not report correct p-values, 33 articles(50%) used mean${\pm}$standard error(mean${\pm}$SE) and 11 articles(l7%) used mean${\pm}$standard deviation(mean${\pm}$SD). Fifty-two articles(95%) of 55 ones which were tested for normal distribution made an error in describing normal distribution. Seventeen articles misused t-test and 12 articles did not carry out the multiple comparison. Conclusions: The training of researchers with clinical statistics or the participation of statisticians in research design will reduce the significant errors in statistical interpretation of the results.

• Child Health Nursing Research
• /
• v.1 no.1
• /
• pp.47-58
• /
• 1995

This study was performed to test the validity and reliability of the Health Self-Determinism Index for Children(HSDI-C), an instrument designed to measure dimensions and strength of motivation in health behavior, to improve the applicability of the tool through application to the various samples. The convenient sample of 148 (boys=75, girls=72 third grade=42, fourth grade=22, fifth grade=32, sixth grade=52 : Caucasian=72, Asian=30, African=19) comprised the children at a chatholic elementary school in Chicago. The children completed English version of HSDI-C from December 5th, 1994 to January l0th, 1995. The findings were as follows : 1. Four factors of HSDI-C were isolated through the principal component analysis and oblique rotation, and explained 48% of the variance in total score. Low correlations among four factors were anticipated because each factor contributed uniquely, All items of the tool loaded above .30 on one of 4 factors. But items loaded on each factor in this study were very different from those in the previous studies. 2. Cronbach's alpha coefficient for internal consistency was .81 for the total items and .57∼ .81 for 4 subscales. 3. The differences of HSDI-c mean scores between boys and girls and that of among races were not statistically signifcant, but the mean score of girls and the Caucasian were relatively high. The total mean score of the scale was highest at the 3rd grade, decreased at the 4th or 5th grade, and reincreased at the 6th grade. The trend of mean score of four subscales was similar to that of total mean score. According to the results, suggested below : 1. The items loaded on each factor in this study were very different from those in the previous studies. To clear away the problem of the conceptual confusion, HSDI-C needs to be performed to various and large samples. 2. Unexpectedly, the HSDI-C mean score decreased at middle school age. A longitudinal study will be helpful to search for the change trend of the intrinsic motivation. 3. To improve the applicabilty of the HSDI-C, various reliability and validity test methods besides factor analysis or internal consistency are recommended.

• Journal of Practical Engineering Education
• /
• v.13 no.2
• /
• pp.293-300
• /
• 2021

The aim of this study was to measure preservice teachers' perceptions of Technological Pedagogical Content Knowledge (TPACK). The researcher analyzed responses on the TPACK scale of 307 students in A University located in Chungcheongbuk-do. During the statistical analysis, IBM SPSS 21 program was used to implement Independent Samples T-test, One-way Analysis of Variance, and Multiple Regression Analysis (Enter method). The results are as follows. First, for the mean difference by gender, the mean of female students was higher than that of male students in Pedagogical Knowledge, Pedagogical Content Knowledge, Technological Pedagogical Knowledge, and Technological Pedagogical Content Knowledge. Second, for the mean difference by grade level, the mean of the 1^st, 3^rd and 4^th graders was higher than that of the 2^nd graders in the Content Knowledge at a statistically significant level. Third, toward Technological Pedagogical Content Knowledge, Pedagogical Knowledge of .11 beta value, Pedagogical Content Knowledge of .11 beta value, and Technological Pedagogical Knowledge of .715 beta value were found to be statistically significant predictors. Finally, the researcher discussed development of the TPACK implementation manual and workbook and provision of various technology practice opportunities.

• Journal of the Korea Society for Simulation
• /
• v.5 no.2
• /
• pp.59-72
• /
• 1996

The purpose of this study is to make an improvement to the batch-means method, which is a procedure to construct a confidence interval(c.i.) for the steady-state process mean of a stationary simulation output process. In the batch-means method, the data in the output process are grouped into batches. The sequence of means of the data included in individual batches is called a batch-menas process and can be treated as an independently and identically distributed set of variables if each batch includes sufficiently large number of observations. The traditional batch-means method, therefore, uses a batch size as large as possible in order to. destroy the autocovariance remaining in the batch-means process. The c.i. prodedure developed and empirically tested in this study uses a small batch size which can be well fitted by a simple ARMA model, and then utilizes the dependence structure in the fitted model to correct for bias in the variance estimator of the sample mean.

• Journal of the Optical Society of Korea
• /
• v.15 no.3
• /
• pp.232-236
• /
• 2011

We analyze the linear equalizers used in optically amplified on-off-keyed (OOK) systems to combat chromatic dispersion (CD) and polarization mode dispersion (PMD), and we derive the mathematical minimum mean squared error (MMSE) performance of these equalizers. Currently, the MMSE linear equalizer for optical OOK systems is obtained by simulations using adaptive approaches such as least mean squared (LMS) or constant modulus algorithm (CMA), but no theoretical studies on the optimal solutions for these equalizers have been performed. We model the optical OOK systems as square-law nonlinear channels and compute the MMSE equalizer coefficients directly from the estimated optical channel, signal power, and optical noise variance. The accuracy of the calculated MMSE equalizer coefficients and MMSE performance has been verified by simulations using adaptive algorithms.

• Transactions of the Korean Society of Mechanical Engineers
• /
• v.19 no.8
• /
• pp.1915-1926
• /
• 1995

The Fatigue characteristics of 8-harness satin woven CFRP composites with a circular hole are experimentally investigated under constant amplitude tension-tension loading. It is found in this study that the fatigue damage accumulation behavior is very random and history-independent, and the fatigue cumulative damage is linearly related with the mean number of cycles to a specified damage state. From these results, it is known that the fatigue characteristics of CFRP composites satisfy the basic assumptions of Markov chain theory and the parameter of Markov chain model can be determined only by mean and variance of fatigue lives. The predicted distribution of the fatigue cumulative damage using Markov chain model shows a good agreement with the test results. For the fatigue life distribution, Markov chain model makes similar accuracy to 2-parameter Weibull distribution function.

• Journal of the Korean Statistical Society
• /
• v.36 no.1
• /
• pp.57-76
• /
• 2007

Kriging is a nonparametric regression method used in geostatistics for estimating curves and surfaces for spatial data. It may come as a surprise that the Kriging estimator, normally derived as the best linear unbiased estimator, is also the solution of a particular variational problem. Thus, Kriging estimators can also be interpreted as generalized smoothing splines where the roughness penalty is determined by the covariance function of a spatial process. We build off the early work by Silverman (1982, 1984) and the analysis by Cox (1983, 1984), Messer (1991), Messer and Goldstein (1993) and others and develop an equivalent kernel interpretation of geostatistical estimators. Given this connection we show how a given covariance function influences the bias and variance of the Kriging estimate as well as the mean squared prediction error. Some specific asymptotic results are given in one dimension for Matern covariances that have as their limit cubic smoothing splines.

• Journal of Institute of Control, Robotics and Systems
• /
• v.12 no.12
• /
• pp.1169-1172
• /
• 2006

The prices of chemical products are fluctuated by several factors. The chemical companies can't predict and be ready to all of these changes, so they are exposed to the risk of a profit fluctuation. But they can reduce this risk by making a well-diversified product portfolio. This problem can be thought as the optimization of the product portfolio. We assume that the profits come from the 'spread' between a naphtha and a chemical product. We calculate a mean and a variation of each spread and develop an automatic module to calculate the optimal portion of each product. The theory is based on the Markowitz portfolio management. It maximizes the expected return while minimizing the volatility. At last we draw an investment selection curve to compare each alternative and to demonstrate the superiority. And we suggest that an investment selection curve can be a decision-making tool.

• Journal of Korean Academy of Nursing
• /
• v.33 no.4
• /
• pp.471-477
• /
• 2003

Purpose. This cross-sectional survey research was undertaken to examine the degree of depression in post-menopausal women and to analyze the factors affecting that depression. Method. 325 people from public health center in Inchon were surveyed as the subject of this study. Data collection was conducted through the use of questionnaires. Results. The above half of these sampled people were in depressed state (64.0%) and the mean score of depression was 12.71. There were significant differences in the depression state according to presence of spouse, economic level, exercise, and smoking. A positive correlation was found between depression and climacteric symptoms. Stepwise multiple regression analysis revealed that the most powerful predictor was climacteric symptom. Climacteric symptom, presence of spouse, smoking, and exercise accounted for 45 % of the variance in postmenopausal women's depression. Conclusion. Nurses are able to use these results to plan and implement nursing interventions for decreasing depression and consequent the improved quality of life in Korean postmenopausal women. Also, the nurses have to be more aware of the following groups; solitary women, low-income group and smokers, that they have higher mean score of depression.

• Nuclear Engineering and Technology
• /
• v.55 no.7
• /
• pp.2712-2722
• /
• 2023

For an accurate and efficient time-dependent Monte Carlo (TDMC) neutron transport analysis, several advanced methods are newly developed and implemented in the Seoul National University Monte Carlo code, McCARD. For an efficient control of the neutron population, a dynamic weight window method is devised to adjust the weight bounds of the implicit capture in the time bin-by-bin TDMC simulations. A moving geometry module is developed to model a continuous insertion or withdrawal of a control rod. Especially, the history-based batch method for the TDMC calculations is developed to predict the unbiased variance of a bin-wise mean estimate. The developed methods are verified for three-dimensional problems in the C5G7-TD benchmark, showing good agreements with results from a deterministic neutron transport analysis code, nTRACER, within the statistical uncertainty bounds. In addition, the TDMC analysis capability implemented in McCARD is demonstrated to search the optimum detector positions for the pulsed-neutron-source experiments in the Kyoto University Critical Assembly and AGN201K.