• Title/Summary/Keyword: Fraction defective

Search Result 34, Processing Time 0.028 seconds

Economic Screening Inspection Plan Under Linear Inspection Error (선형검사과오(線型檢査過誤)를 고려한 최소비용(最少費用)의 선별검사방식(選別檢査方式))

  • Kim, Gwang-Seop;Hwang, Ui-Cheol
    • Journal of Korean Society for Quality Management
    • /
    • v.16 no.2
    • /
    • pp.82-91
    • /
    • 1988
  • This study is concerned with the development of the economic sampling inspection plan when it is possible to carry out a nondestructive screening inspection for the rejected lots by substitutive characteristics closely related to the original quality characteristic. It is assumed that the probabilities of those errors depend linearly on the fraction defective of the process. The inspection policies considered are as follows: take a random sample of size n from the lot of size N and perform a destructive test on the sample. If the number of the defective items is not greater than a critical number C, accept the lot. Expected cost functions are obtained when the process average can be considered to follow a beta distribution and the way of finding the optimal values of (n, c) is to be explored.

  • PDF

Apparent and True Proportions (겉보기 비율과 참비율에 관한 연구)

  • Chang, Kyung
    • Journal of the Korea Safety Management & Science
    • /
    • v.18 no.2
    • /
    • pp.119-125
    • /
    • 2016
  • The ratio which we usually use in producing products is nonconforming proportion or percent defective. As our modern society develops, we cannot but meet another proportion in legal, managerial, and medical areas where our human beings might commit various kinds of errors though they do not want them. In this paper we will generally call the ratio 'proportion.' When the size of such proportion as percent defective is observed by persons, it is not true proportion but apparent proportion because it has been observed with human or situational errors. Past studies have not systematically covered the analysis of relations between such proportions and type 1 and 2 error, but this paper analyses and derives such various relations, and it suggests the guideline as sixteen properties for utilization and sensitive analysis of the relations. Current paper's consideration of apparent proportion in addition to true proportion as our familiar concept will open and widen existing academic and application areas where people have mainly built societal, scientific and engineering rules and methods based only on true proportion.

Minimization Models of Defective Product Inventory Cost (불량품(不良品)을 고려(考慮)한 재고비용(在庫費用) 최소화(最小化) 모형(模型))

  • Kim, Jae-Ryeon;Yu, Seung-Ho
    • Journal of Korean Society for Quality Management
    • /
    • v.16 no.2
    • /
    • pp.92-98
    • /
    • 1988
  • In this paper a model is developed for an inventory system in which the number of units of acceptable quality in a replenishment lot is uncertain and the demand. during the stockout period is back ordered and. also under the same condition an inventory model with experdited stockout is developed. It is assumed that the fraction of the acceptable quality in a replenishment lot is a random variable whose probability distribution is known. The optimal replenishment policy is synthesized for such a system. A numerical example is used to illustrate the theory.

  • PDF

Design of Economic Screening Inspection Plan for Protecting Given LTPD (LTPD보증을 위한 경제적선별검사방식의 설계)

  • 김광섭
    • Journal of Korean Society of Industrial and Systems Engineering
    • /
    • v.11 no.18
    • /
    • pp.27-34
    • /
    • 1988
  • This study is concerned with the development of the economic sampling inspection plan when it is possible to carry out a nondestructive screening inspection for the rejected lots by substitutive characteristics closely related to the original quality characteristic. It is assumed that the probabilities of those errors depend linearly on the fraction defective of the process sampling inspection policy for isolated lot is studied where the probability of accepting the lot with bad quality from the results of sampling inspection is restricted to be small.

  • PDF

Selection Problems in terms of Coefficients of Vairiation

  • Park, Chi-Hoon;Jeon, Jong-Woo;Kim, Woo-Chul
    • Journal of the Korean Statistical Society
    • /
    • v.11 no.1
    • /
    • pp.12-24
    • /
    • 1982
  • Selection procedures are proposed for selecting the 'best' industrial process with the smallest fraction defective. For normally distributed industrial processes, this is equivalent to selecting in terms of coefficients of variation. For the case of known vairances, selection procedures by Bechhofer (1954), and Bechhofer and Turnball (1978) are appropriate. We treat this problem for the case of uknown variances with or without reference to a standard. The large sample solutions of design constants are tabulated and the performance of these approximate solutions are investigated.

  • PDF

Exponentially Weighted Moving Average Control Charts for Counted Data (계수치 데이터를 위한 EWMA 관리도)

  • An, Dong-Geun;Jang, Joong-Soon
    • Journal of Korean Society for Quality Management
    • /
    • v.22 no.4
    • /
    • pp.13-27
    • /
    • 1994
  • This study is concerned with design of EWMA control charts for counted data. Control charts for the fraction defective and the number of defects are designed. Performance analysis is accomplished for validity of the designed EWMA control charts. Average run length(ARL) is adopted as a criterion for comparison. Simulation results show that the designed EWMA control charts have shorter ARL than pn, p and c control charts when the fraction nonconforming or the average defect number are shifted. This means that the designed control charts can detect the out of -control state of the process more fastly than the traditional control charts.

  • PDF

Optimal Inspection Policy in an Economic Production Quantity with Random Defectives (불량품을 갖는 경제적 생산량 모델의 최적 검사 정책에 관한 연구)

  • Jo, Jae-Rip
    • Journal of Korean Society for Quality Management
    • /
    • v.20 no.2
    • /
    • pp.1-10
    • /
    • 1992
  • In this paper, we study a joint lot sizing and inspection policy under an EPQ(Economic Production Quantity) model where a random proportion of units are defectives. Those units can be discovered only through costly inspection. The problem is thus bivariate : both lot size and fraction to inspect are to be chosen. We first analyze a model in which the only penalty for uninspected defectives is financial, and then consider a model where defectives units cannot be used and thus must be replaced by non-defective ones. As a result it can be proved that this inspection policy costs economically and is to be decided effectively for the Economic Production Quantity constraining the fraction to inspect.

  • PDF

Quality Improvements of Breast Specimen Fixation for Histopathology Test (병리검사를 위한 유방검체 고정의 질 향상 활동)

  • Cho, Seong-Il;Choi, Myung-Sup;Bae, Moon-Hwan;Lee, Moon-Jung;Woo, Hee-Suck;Park, Soon-Chae;Cho, Eun-Yoon
    • Korean Journal of Clinical Laboratory Science
    • /
    • v.42 no.3
    • /
    • pp.149-154
    • /
    • 2010
  • To improve accuracy of the immunohistochemical testing and fluorescence in situ hybridization (FISH) study as well as a routine histology diagnosis in breast cancer, quality improvement for optimal tissue handling is mandatory. We evaluate fraction defective of 7107 blocks from 349 breast cancer patients, who underwent surgical treatment at Samsung Medical Center Seoul, Korea from January 1, 2009 to March 31, 2010. We decided pre-improvement period from January, 2009 to June, 2009. In the first quality improvement period (July, 2009 to September, 2009) we made improvements in protocol of gross examination. In the second quality improvement period (October, 2009 to December, 2009) we attempted more effective formalin fixation such as frequent exchange of formalin and use of separate fixation container for each case. In the third quality improvement period (January, 2010 to March, 2010) improvement of tissue processor was performed. We achieved a marked reduction of fraction defective (9-16%) through efforts to improve quality of formalin-fixed, paraffin-embedded blocks when compared to pre-improvement period.

  • PDF

A Study on the Machine Selection Problem Considering the Cost of Defective Products in the Machining Process (절삭가공에서의 불량가공비용을 고려한 기계선정에 관한 연구)

  • Park, Chan-Woong
    • Journal of Digital Convergence
    • /
    • v.12 no.8
    • /
    • pp.345-350
    • /
    • 2014
  • The most important decision of process planning for the manufacturing system is the machine selection problem to minimize machining costs. Each machine has its own different machining performance indicating a different fraction of scrap, making the cost of scrap generated by machining is different for each machine. Therefore, when we decide on machine selection, we must consider the machining cost and the cost of scrap generated. This paper describes the statistical model for the fraction of scrap generated by machining and the machine selection algorithm considering the total cost including the machining cost and the cost of scrap generated.

Rhizobium meliloti 102F51 Mutants Defective in Heme Synthesis (Heme 합성특성이 다른 Rhizobium meliloti 102F51 Mutant의 선별)

  • 최영주;정원화;김경수;신평균;조무제
    • Korean Journal of Microbiology
    • /
    • v.24 no.2
    • /
    • pp.98-105
    • /
    • 1986
  • Rhizobium meliloti 102 F 51, the symbiotic partner of alfalfa, was mutagenized with N-methyl-N'-nitro-N-nitrosoguanidine (NTG) and UV-irradiation. Three group of mutants which form white, white-pink and red nodules were selected. The adetylene reduction activity, nodulation activity, amount of heme synthesis during the nodulation, and ${\delta}-aminolevulinic$ acid synthetase (ALAS) and ${\delta}-aminolevulinic$ acid dehydratase (ALAD) activities in free living rhizobia and bacteroid states of the each group of mutants were compared. The mutants forming white nodules showed lower acetylene reduction activity compared to those of red nodule forming mutants. The two key enzymes for the heme synthetic pathway, ALAS and ALAD activities of the mutants forming red nodules was much higher than those of the mutants forming white nodules in bacteroid state, however no significant difference was observed in free living state. In the nodules the ALAS was detected only in bacteroid fraction, while ALAD was detected both in bacteroid and plant fraction. ALAS was dramatically increased with the heme synthesis during the nodulation, while ALAD was decreased in plant fraction but slight increase was observed in bacteroid fraction.

  • PDF