• Journal of Korean Society for Quality Management
• /
• v.22 no.4
• /
• pp.1-12
• /
• 1994

For quality improvement, Taguchi emphasizes the reduction of variation of the quality characteristic. Taguchi has used the signal to noise ratios for achieving minimum dispersion of the quality characteristic with its location adjusted to some desired target value. At each setting of design factors, the variance of the quality characteristic could be affected by the mean. In most cases, as the mean get larger, the variance tends to increase, The Taguchi's SN ratio corresponds to the case that the variance is proportional to the square of the mean. But the variance can increase faster or slower than the square of the mean. We propose to infer a linking relationship of the variance and mean through simple data analysis technique, and then use a reasonable SN ratio.

• Journal of Korean Society for Quality Management
• /
• v.30 no.1
• /
• pp.118-132
• /
• 2002

This paper presents a process incapability index to provide manager with various information of process and to reduce cost. The introduced process incapability indices indicate information about mean and variance of manufacturing process and variance of inspection process to evaluate process capability using ratio of variance and difference between target and mean to specification. This model can be used by the scale of six sigma management.

• Journal of the Korean Statistical Society
• /
• v.26 no.2
• /
• pp.199-210
• /
• 1997

Using regression methods based on quasi-likelihood equation, one only needs to specify the conditional mean and variance functions for the response variable in the analysis. In this paper, an omnibus lack-of-fit test is proposed to test the validity of these two functions. Our test is consistent against the alternative under which either the mean or the variance is not the one specified in the null hypothesis. The large-sample null distribution of our test statistics can be approximated through simulations. Extensive numerical studies are performed to demonstrate that the new test preserves the prescribed type I error probability. Power comparisons are conducted to show the advantage of the new proposal.

• Korean Management Science Review
• /
• v.13 no.1
• /
• pp.47-55
• /
• 1996

Rapid globalization of production and marketing functions makes choice of international transportation mode of great importance. In this paper, transportation mode is characterized by two factors, mean and variability of transportation lead time. We developed a simple mathematical model to estimate the relative impact of mean lead time, lead time variance and demand variance on the required average inventory level under specified service rates.

• 한국해양학회지
• /
• v.21 no.4
• /
• pp.193-202
• /
• 1986

Spatio-temporal variabilities of seawater temperature at 0 and 30m in the southeastern Hwanghae were studied by variance and empirical orthogonal function(EOF) analysis of long records of temperature between 1967 and 1982. The spatial distribution of monthly mean sea surface temperature has a pattern similar to the long-term annual mean which decreases from south to north. On the contrary, the total variance computed from the annual mean of sea surface temperature(SST) increases from south to north. The variance of SST is found to be two times greater than that at 30m in the study area except coastal area south of Kyunggi Bay. The important variance of temperature seem s to be closely associated with the seasonal change of temperature because the first and second modes of EOF having a seasonal cycle explain 97.6% and 85.2% of variances at 0 and 30m, respectively. There is a large difference in temperature between the northern and southern parts of the study area during winter, while the difference becomes very small during summer. This might reflect that in summer the heat gain of sea surface from the incoming radiation is much more important than the heat loss or the oceanic heat advection. In summer coastal waters south of the Kyunggi Bay and around Mokpo are observed to be colder than offshore waters due to tidal mixing.

• Korean Journal of Food Science and Technology
• /
• v.26 no.1
• /
• pp.57-61
• /
• 1994

Performance of panelists trained for cooked rice quality was evaluated using analysis of variance, correlation analysis, and principal component analysis. Each method offered different information. Results showed that panleists with high F ratios (p=0.05) did not always have high correlation coefficient (p=0.05) with mean values pooled from whole panel. The results of analysis of variance for the panelists whose performance were extremely good or extremely poor were consistent with those of correlation analysis. Outliers designated by principal component analysis were different from the panelists whose performance was defined as extremely good or extremely poor by analysis of variance and correlation analysis. The results of principal component analysis descriminated the panelists with different scoring range more than different scoring trends depending on the treatments. Our study suggested combination of analysis of variance and correlation analysis provided valid basis for screening panelists.

• Industrial Engineering and Management Systems
• /
• v.16 no.1
• /
• pp.22-43
• /
• 2017

It is urgently-needed to construct a green supply chain (GSC) from collection of used products through recycling of them to sales of products using the recycled parts. Besides, it is necessary to consider the uncertainty in product demand as a risk in a GSC. This study proposes the optimal operations for a GSC with a retailer and a manufacturer. A retailer pays an incentive for collection of used products from customers and sells a single type of products in a market. A manufacturer produces the products ordered by the retailer, using recyclable parts with acceptable quality and compensates the collection cost of used products as to the recycled parts. This paper discusses the following risk attitudes: risk-neutral attitude, risk-averse attitude, and risk-prone attitude. Using mean-variance analysis, the optimal decisions for product order quantity, collection incentive, and lower limit of quality level, in the decentralized GSC (DGSC) and the integrated GSC (IGSC) are made. DGSC optimizes the utility function of each member. IGSC does that of the whole system. The analysis numerically investigates how (i) risk attitude and (ii) quality of recyclable parts affect the optimal operations. Supply chain coordination between GSC members to shift IGSC from DGSC is discussed.

• Phonetics and Speech Sciences
• /
• v.11 no.3
• /
• pp.23-29
• /
• 2019

This study acoustically examines the quality of fricatives produced by ten dysarthric speakers with cerebral palsy. Previous similar studies tend to focus only on sibilants, but to obtain a better understanding of how dysarthria affects fricatives we selected a range of samples with different places of articulation and voicing. The Universal Access (UA) Speech database was used to select thirteen words beginning with one of the English fricatives (/f/, /v/, /s/, /z/, /ʃ/, /ð/). The following four measurements were taken for both dysarthric and healthy speakers: phoneme duration, mean spectral peak, variance and skewness. Results show that even speakers with mild dysarthria have significantly longer fricatives and a lower mean spectral peak than healthy speakers. Furthermore, mean spectral peak and variance showed significant group effects for both healthy and dysarthric speakers. Mean spectral peak and variance was also useful for discriminating several places of articulation for both groups. Lastly, spectral measurements displayed important group differences when taking severity into account. These findings show that in general there is a degradation in the production of fricatives for dysarthric speakers, but difference will depend on the severity of dysarthria along with the type of measurement taken.

• Journal of Applied Reliability
• /
• v.11 no.3
• /
• pp.213-224
• /
• 2011

In this paper, we analyze statistically the data set of first leak time of water pipeline. We classify first the leak time data by pipe type, location, diameter of pipe and, length of pipe. We perform the analysis of variance to indicate that there are significant difference of mean of the time between levels of the factor and also compare the distribution of levels using the multiple box-plot. When there are the difference of the mean, we perform the least significant test to find out what levels of the facor has a different mean.

• Journal of the Korean Operations Research and Management Science Society
• /
• v.13 no.1
• /
• pp.47-47
• /
• 1988

Rapid globalization of production and marketing functions makes choice of international transportation mode of great importance. In this paper, transportation mode is characterized by two factors, mean and variability of transportation lead time. We developed a simple mathematical model to estimate the relative impact of mean lead time, lead time variance and demand variance on the required average inventory level under specified service rates.