Journal of The Japanese Society for Quality Control
Online ISSN : 2432-1044
Print ISSN : 0386-8230
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Volume 29, Issue 4
Displaying 1-11 of 11 articles from this issue
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Research Papers
Contributed Paper
  • Estimation of Conditional Intervention Effect in Adaptive Control
    Manabu KUROKI, Masami MIYAKAWA
    Article type: Contributed Paper
    1999 Volume 29 Issue 4 Pages 70-80
    Published: October 15, 1999
    Released on J-STAGE: October 20, 2018
    DOIhttps://doi.org/10.20684/quality.29.4_70
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    Consider the case where a causal diagram with a linear structural equation model is used to describe cause-effect relationships between a response and explanatory variables. In order to control the response, the level of some treatment may be changed by external intervention corresponding to states of environment or materials. It is essential to distinguish a set of covariates for the control from a set of covariates for the identification in causal diagrams in order to design the adaptive control. The effect of conditional intervention for variance of the response is investigated by using the linear structural equation model. The conditional intervention plan which minimizes the variance can is formulated. Covariate selection criteria for identifying the causal effect are also given.
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Technical Note
  • Constructing Control Limits of X- s2 Charts Using Bootstrap Methods
    Hideo SUZUKI, Naoki SHINODA
    Article type: Technical Note
    1999 Volume 29 Issue 4 Pages 81-96
    Published: October 15, 1999
    Released on J-STAGE: October 20, 2018
    DOIhttps://doi.org/10.20684/quality.29.4_81
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    Shewhart control charts are based on a fundamental assumption that quality characteristic variables are independent and normally distributed when a process is in a state of statistical control, or in control. In practice, however, the distribution of the variables being measured may be strongly skewed. The bootstrap method is a powerful computer-based method that can provide control charts without the usual normal-theory assumptions. This paper proposes techniques for constructing control limits of X^^--s^2 charts from well-known bootstrap confidence intervals, such as the BC_a (bias-corrected and accelerated), ABC (approximate bootstrap confidence intervals) and Bootstrap-t method. These bootstrap methods have not been used in published papers for bootstrap control charts. We provide simulation studies and evaluate the performance of two conventional control charts (the standard and simple percentile bootstrap control charts) and these bootstrap control charts based on the difference between the estimated control limits and the true control limits. The results show that the percentile and BC_a methods for X^^--s^2 charts perform comparatively better than the standard method when the process distribution is skewed. The control limits estimates for the ABC and Bootstrap-t methods are less accurate than those for the other methods that were examined. In particular, the Bootstrap-t method estimates for the s^2 charts is found to be unreliable
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Survey and Field Study
  • New TQM's Approach to Solve Problems of the Past TQC
    KAZUO TAKAHASHI, Daisuke IWADARE, Masumi AKITA, Hiroshi OSADA, Syohei ...
    Article type: Survey and Field Study
    1999 Volume 29 Issue 4 Pages 97-106
    Published: October 15, 1999
    Released on J-STAGE: October 20, 2018
    DOIhttps://doi.org/10.20684/quality.29.4_97
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    After the TQC movements in the 1980s, TQC activities were reviewed and many problems about TQC were found. Through these studies, the new concept of TQM is being configured. However the relationship between the problems of TQC and the concept of TQM is not clear. It is difficult to understand what problems of TQC are solved in the TQM, and what problems should be considered in TQM. One of the main aims of this paper is to clarify the relationship between the problems of TQC and the concept of TQM and make TQM more useful. In this paper, first we survey the articles in the main journals on TQC published in 1990s. We extract the problems of TQC from the articles and make knowledge pieces of the problems. The knowledge pieces are statements about the problems of TQC in the articles. Next, we classify the problems by the grouping method of CDM^<TM> which is similar to the KJ method. Finally we clarify the relationship between the classified problems and the concept of TQM. This study will indicate us what should necessarily be for the new TQM, and give us a concrete shape of TQM concept.
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Applied Research
  • A Method of Selecting Image Items for the Misunderstanding-proneness Evaluation of Safety Symbols Using Variance of Images
    Takeshi NAKAJO, Tsuyoshi SAKAMOTO, Tomozo UCHIDA
    Article type: Applied Research
    1999 Volume 29 Issue 4 Pages 107-115
    Published: October 15, 1999
    Released on J-STAGE: October 20, 2018
    DOIhttps://doi.org/10.20684/quality.29.4_107
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    T. Uchida et al. investigated a method of evaluating misunderstanding-proneness of displays based on the variance of images received from the displys. What image items should be used in this method, however, is not investigated. This paper focused on safety symbols and experimentally identified which image items should be used in the evaluation. According to results, images items which directly ask evaluation of the display:i.e., "is it familiar for you?" and "is it easy for you to understand?" and those which ask contents of the message received from the display:i.e., "do you feel it is important?" and "do you feel it is related to being alive/dead?" are effective. Moreover, the unbalance between variances of paired image items is closely related to the misunderstanding-proneness of displays.
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