• Journal of Korean Society for Quality Management
• /
• v.22 no.1
• /
• pp.54-65
• /
• 1994

Multivariate exponentially weighted moving average (EWMA) control charts for monitoring the variance-covariance matrix are investigated. Two basic approaches, "combine-accumulate" approach and "accumulate-combine" approach, for using past sample information in the developement of multivariate EWMA control charts are considered. Multivariate EWMA control charts for monitoring the variance-covariance matrix are compared on the basis of their average run length (ARL) performances. The numerical results show that multivariate EWMA control charts based on the accumulate-combine approach are more efficient than corresponding multivariate EWMA control charts based on the combine-accumulate approach.

• Journal of Korean Society for Quality Management
• /
• v.25 no.1
• /
• pp.100-115
• /
• 1997

Shewhart control chart is a basic technique to monitor the state of a process. We observe samples of size four or five and plot some statistic(e.g., mean or range) of each sample on the chart. When setting up the chart, we need to obtain u, pp.r and lower control limits. It is common practice that those limits are calculated from the preliminary 20-40 samples presumed to be homogeneous. However, it may ha, pp.n in practice that the samples are contaminated by outlying observations caused by various reasons. The presence of outlying observations make the control limits wider and hence decrease the sensitivity of the charts. In this paper, we introduce robust control charts with tighter control limits when outlying observations are present in the preliminary samples. Examples will be given via simulation study.

• Journal of applied mathematics & informatics
• /
• v.3 no.2
• /
• pp.253-264
• /
• 1996

The generalized logit model of nominal type with random regressors is studied for bootstrapping. We assess the accuracy of some estimators for our generalized logit model using a Monte Carlo simu-lation. That is we study the finite sample properties containing the consistency and asymptotic normality of the maximum likelihood es-timators. Also we compare Newton Raphson algorithm with BHHH algorithm.

• Culinary science and hospitality research
• /
• v.23 no.3
• /
• pp.29-37
• /
• 2017

This study investigated the physicochemical and sensory characteristics of white bean paste prepared with various amounts of aronia powder (as ratios of 0%, 2%, 4%, 6%, 8%, 10%). The result shows that the pH of white bean paste decreased significantly with the addition of aronia powder. From chromatography, the brightness, L-value was decreased by increasing the adding rate of aronia powder. The a-value of sample group adding 2% of aronia powder was the highest and that of sample group adding 8% was the lowest (p<0.01). Sample group adding 8% of aronia powder achieved the highest appraisal from many factors, such as springiness, cohesiveness, chewiness, brittleness, and adhesiveness. The total polyphenols and anthocyanin contents were proportionally increased with increasing the level of aronia powder added in white bean paste. The antioxidant activity measured by DPPH and NSA radical scavenging activities was significantly higher than control and increased proportionally to the aronia powder concentration. The result of sensory test shows that sample group adding 6% of aronia powder achieved the highest. Based on the above results, this study suggests that the addition of 6% aronia powder may be the best substitution ratio for white bean paste of the improvement of sensory preference and antioxidant.

• Korean Journal of Clinical Laboratory Science
• /
• v.52 no.4
• /
• pp.381-388
• /
• 2020

The quality control of pathological specimens is important for accurate molecular pathology testing. This study evaluated that specimen factors affecting the DNA quality during tissue processing and sample types for BRAF, EGFR, and KRAS mutations tests. One thousand seven hundred and seventy-two molecular pathology tests were investigated for the factors influencing the DNA quality, such as sample type, formalin fixation time, and reexamination status. Cytology samples stored in a saline solution had better DNA quality than commercial cytology preservation. Tissue samples fixed in formalin within 24 hours had better DNA quality than the samples fixed over 24 hours. Between the types of samples, fresh tissue samples and tissue samples with a high tumor cell density had relatively better DNA quality than the formalin-fixed paraffin-embedded (FFPE) tissues and cytology specimens. Of real-time PCR, the non-PNA Ct value increased proportionally with samples held for longer than 24 hours in formalin, and that the formalin-fixed time affects the sample DNA quality. In conclusion, the appropriate tumor cellularity and 10% neutral formalin fixation time are the most important factors for maintaining the DNA quality. These factors should be managed properly for an accurate pathological molecular test to ensure optimal DNA quality.

• Journal of Korean Society for Quality Management
• /
• v.32 no.1
• /
• pp.92-101
• /
• 2004

Tris paper present an economic statistical design which have statistically constraints for the optimal design of an EWMA control charts with variable sampling interval. Cost function use that proposed by Lorenzen and Vance, and the optimal design parameters include the sample size, control limit width, sampling interval, EWMA weight value. Comparisons between VSI EWMA control charts optimal economic design and optimal economic statistical designs show the following fact. Although have demerits which are more costly than economic design, have merits which to detect shifts more efficiently and to improve statistical performance.

• Journal of the Korean Operations Research and Management Science Society
• /
• v.31 no.3
• /
• pp.127-143
• /
• 2006

While e-learners' satisfaction would be determined by qualify of e-learning environment including learning management systems, learning contents and interactions, the influence of quality on satisfaction can be changed by e-learners' self-regulated efficacy The objective of this study is to show difference of the relationship between qualify and satisfaction In e-learning by self-regulated efficacy. For this purpose, we propose a research model which consists of five quality factors in e-learning as explaining variables, satisfaction as a result variable and self-regulated efficacy as a control variable. For empirical test of this model, the sample is collected from e-learning classes in a college and divided into two groups by self-regulated efficacy in order to analyze the effects of control variable. By multi-group analysis, we show two groups are different from each other in the relationship between quality and satisfaction of e-learning environment.

• Journal of Korean Society for Quality Management
• /
• v.15 no.2
• /
• pp.10-19
• /
• 1987

Statistical control charts are useful tools to monitor and control the manufacturing processes and are widely used in most Korean industries. Many Korean companies, however, do not always obtain desired results from the traditional control charts by Shewhart such as the $\overline{X}$-chart, X-chart, $\widetilde{X}$-chart, etc. This is partly because the quality charterstics of the process are not distributed normally but are skewed due to the intermittent production, small lot size, etc. In the Shewhart $\overline{X}$-chart, which is the most widely used one in Korea, such skewed distributions make the plots to be inclined below or above the central line or outside the control limits although no assignable causes can be found. To overcome such shortcomings in nonnormally distributed processes, a distribution-free type of confidence interval can be used, which should be based on order statistics. This thesis is concerned with the design of control chart based on a sample median which is easy to use in practical situation and therefore properties for nonnormal distributions may be easily analyzed. Control limits and central lines are given for the more famous nonnormal distributions, such as Gamma, Beta, Lognormal, Weibull, Pareto, and Truncated-normal distributions.

• Journal of the Korean Society of Food Culture
• /
• v.21 no.3
• /
• pp.290-296
• /
• 2006

Physicochemical and sensory characteristics of the walnut bread with various levels of resistant starch were investigated in this study. Water contents of dough had significantly the largest value of 44.91% with 10% substituted sample group and the control group had significantly the lowest value (p<0.05). Volume of 10 and 20% substituted sample groups and control group were not significantly different. The 10 and 20% substituted groups had significantly the lower hardness compared to those of control group. Results of sensory characteristics showed significantly higher savory aroma, astringent flavor with 30% substituted sample group at p<0.05. Savory aroma was not significantly different among the walnut breads. Acceptance test of walnut bread with 10% substituted sample group showed the higher appearance, savory flavor, texture, and overall acceptability and they did not show significant differences with the 20% substituted sample groups. Quality characteristics of walnut bread with 10% and 20% substituted sample groups indicated significantly similar or higher values compared to those of control.

• Journal of the Korean Home Economics Association
• /
• v.30 no.3
• /
• pp.119-129
• /
• 1992

Black soybeans were gamma-irradiated at dost levels of 0, 2., 5, 10 and 20 kGy, and stored at room temperature for the experiments associated with cooking quality. The degree of cooking of soybeans in boiling water at 98-10$0^{\circ}C$ has been determined by measuring the maximum cutting force of cotyledon. The cutting force to reach a complete cooking was about 120~130g/g. Irradiation at 2.5~20kGy caused the reduction of cooking time in black soybeans by 30~60% compared to the nonirradiated control, and the cooking rate constant of the irradiated samples was higher than that fo the nonirradiated control sample. These results were similarly found in the stored samples for one year at room temperature after irradiation. Color characteristics of cooked samples showed no significant difference between the nonirradiated control and 5 kGy-irradiated sample. After complete cooking of black soybeans, there were not significant in the organoleptic qualities between the nonirradiated and irradiated samples.