Includes bibliographical references (pages 165-169). / Classical Statistical Process Control Charts are essential in Statistical Control exercises and thus constantly obtained attention for quality improvements. However, the establishment of control charts requires large-sample data (say, no less than I 000 data points). On the other hand, we notice that the small-sample based Grey System Theory Approach is well-established and applied in many areas: social, economic, industrial, military and scientific research fields. In this research, the short time trend curve in terms of GM( I, I) model will be merged into Shewhart and CU SUM two-sided version control charts and establish Grey Predictive Shewhart Control chart and Grey Predictive CUSUM control chart. On the other hand the GM(2, I) model is briefly checked its of how accurate it could be as compared to GM( I, 1) model in control charts. Industrial process data collected from TBF Packaging Machine Company in Taiwan was analyzed in terms of these new developments as an illustrative example for grey quality control charts.

No description available.

Assignment (MSc)--Stellenbosch University, 2004. / ENGLISH ABSTRACT: The design of control charts refers to the selection of the parameters implied, including the sample size n, control limit width parameter k, and the sampling interval h. The design of the X -control chart that is based on economic as well as statistical considerations is presently one of the more popular subjects of research. Two assumptions are considered in the development and use of the economic or economic statistical models. These assumptions are potentially critical. It is assumed that the time between process shifts can be modelled by means of the exponential distribution. It is further assumed that there is only one assignable cause. Based on these assumptions, economic or economic statistical models are derived using a total cost function per unit time as proposed by a unified approach of the Lorenzen and Vance model (1986). In this approach the relationship between the three control chart parameters as well as the three types of costs are expressed in the total cost function. The optimal parameters are usually obtained by the minimization of the expected total cost per unit time. Nevertheless, few practitioners have tried to optimize the design of their X -control charts. One reason for this is that the cost models and their associated optimization techniques are often too complex and difficult for practitioners to understand and apply. However, a user-friendly Excel program has been developed in this paper and the numerical examples illustrated are executed on this program. The optimization procedure is easy-to-use, easy-to-understand, and easy-to-access. Moreover, the proposed procedure also obtains exact optimal design values in contrast to the approximate designs developed by Duncan (1956) and other subsequent researchers. Numerical examples are presented of both the economic and the economic statistical designs of the X -control chart in order to illustrate the working of the proposed Excel optimal procedure. Based on the Excel optimization procedure, the results of the economic statistical design are compared to those of a pure economic model. It is shown that the economic statistical designs lead to wider control limits and smaller sampling intervals than the economic designs. Furthermore, even if they are more costly than the economic design they do guarantee output of better quality, while keeping the number of false alarm searches at a minimum. It also leads to low process variability. These properties are the direct result of the requirement that the economic statistical design must assure a satisfactory statistical performance. Additionally, extensive sensitivity studies are performed on the economic and economic statistical designs to investigate the effect of the input parameters and the effects of varying the bounds on, a, 1-f3 , the average time-to-signal, ATS as well as the expected shift size t5 on the minimum expected cost loss as well as the three control chart decision variables. The analyses show that cost is relatively insensitive to improvement in the type I and type II error rates, but highly sensitive to changes in smaller bounds on ATS as well as extremely sensitive for smaller shift levels, t5 . Note: expressions like economic design, economic statistical design, loss cost and assignable cause may seen linguistically and syntactically strange, but are borrowed from and used according the known literature on the subject. / AFRIKAANSE OPSOMMING: Die ontwerp van kontrolekaarte verwys na die seleksie van die parameters geïmpliseer, insluitende die steekproefgrootte n , kontrole limiete interval parameter k , en die steekproefmterval h. Die ontwerp van die X -kontrolekaart, gebaseer op ekonomiese sowel as statistiese oorwegings, is tans een van die meer populêre onderwerpe van navorsing. Twee aannames word in ag geneem in die ontwikkeling en gebruik van die ekonomiese en ekonomies statistiese modelle. Hierdie aannames is potensieel krities. Dit word aanvaar dat die tyd tussen prosesverskuiwings deur die eksponensiaalverdeling gemodelleer kan word. Daar word ook verder aangeneem dat daar slegs een oorsaak kan wees vir 'n verskuiwing, of te wel 'n aanwysbare oorsaak (assignable cause). Gebaseer op hierdie aannames word ekonomies en ekonomies statistiese modelle afgelei deur gebruik te maak van 'n totale kostefunksie per tydseenheid soos voorgestel deur deur 'n verenigende (unified) benadering van die Lorenzen en Vance-model (1986). In hierdie benadering word die verband tussen die drie kontrole parameters sowel as die drie tipes koste in die totale kostefunksie uiteengesit. Die optimale parameters word gewoonlik gevind deur die minirnering van die verwagte totale koste per tydseenheid. Desnieteenstaande het slegs 'n minderheid van praktisyns tot nou toe probeer om die ontwerp van hulle X -kontrolekaarte te optimeer. Een rede hiervoor is dat die kosternodelle en hulle geassosieerde optimeringstegnieke té kompleks en moeilik is vir die praktisyns om te verstaan en toe te pas. 'n Gebruikersvriendelike Excelprogram is egter hier ontwikkel en die numeriese voorbeelde wat vir illustrasie doeleindes getoon word, is op hierdie program uitgevoer. Die optimeringsprosedure is maklik om te gebruik, maklik om te verstaan en die sagteware is geredelik beskikbaar. Wat meer is, is dat die voorgestelde prosedure eksakte optimale ontwerp waardes bereken in teenstelling tot die benaderde ontwerpe van Duncan (1956) en navorsers na hom. Numeriese voorbeelde word verskaf van beide die ekonomiese en ekonomies statistiese ontwerpe vir die X -kontrolekaart om die werking van die voorgestelde Excel optimale prosedure te illustreer. Die resultate van die ekonomies statistiese ontwerp word vergelyk met dié van die suiwer ekomomiese model met behulp van die Excel optimerings-prosedure. Daar word aangetoon dat die ekonomiese statistiese ontwerpe tot wyer kontrole limiete en kleiner steekproefmtervalle lei as die ekonomiese ontwerpe. Al lei die ekonomies statistiese ontwerp tot ietwat hoër koste as die ekonomiese ontwerpe se oplossings, waarborg dit beter kwaliteit terwyl dit die aantal vals seine tot 'n minimum beperk. Hierbenewens lei dit ook tot kleiner prosesvartasie. Hierdie eienskappe is die direkte resultaat van die vereiste dat die ekonomies statistiese ontwerp aan sekere statistiese vereistes moet voldoen. Verder is uitgebreide sensitiwiteitsondersoeke op die ekonomies en ekonomies statistiese ontwerpe gedoen om die effek van die inset parameters sowel as van variërende grense op a, 1- f3 , die gemiddelde tyd-tot-sein, ATS sowel as die verskuiwingsgrootte 8 op die minimum verwagte kosteverlies sowel as die drie kontrolekaart besluitnemingsveranderlikes te bepaal. Die analises toon dat die totale koste relatief onsensitief is tot verbeterings in die tipe I en die tipe II fout koerse, maar dat dit hoogs sensitief is vir wysigings in die onderste grens op ATS sowel as besonder sensitief vir klein verskuiwingsvlakke, 8. Let op: Die uitdrukkings ekonomiese ontwerp (economic design), ekonomies statistiese ontwerp (economic statistical design), verlies kostefunksie (loss cost function) en aanwysbare oorsaak (assignable cause) mag taalkundig en sintakties vreemd voordoen, maar is geleen uit, en word so gebruik in die bekende literatuur oor hierdie onderwerp.

published_or_final_version / Surveying / Master / Master of Science in Construction Project Management

This study was a follow up to P. C. Dams' (1996) unpublished University of North Texas masters thesis, The effect of defect probability during training on inspection accuracy in a quality control simulation. Graphics of computer circuit boards were presented in dyads with an error free sample on the left and a comparison on the right. Comparisons had either a rotation or transposition defect, or were error free. Subjects had 10-s to accept or reject the comparison as identical to the sample. They were trained using two different stimulus fading procedures (using descending defect probabilities) and immediate feedback. Defect probabilities for the Tens were 0.60, 0.50, 0.40, and 0.30 and for the Twenties were 1.00, 0.80, 0.60, and 0.40. The last 4 pretraining and posttraining sessions were compared and the posttraining performance of the Twenties, as compared to the Tens, demonstrated greater improvement over pretraining performance. No firm conclusions could be drawn as to the effectiveness of either training procedure. The significance of the current investigation and suggestions for future research are discussed.

歐樹軍. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2009. / Includes bibliographical references (leaves 238-253) / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstracts in Chinese and English. / Ou Shujun.

When the nonconformities are independent, a multivariate control chart for nonconformities called a demerit control chart using a distribution approximation technique called an Edgeworth Expansion, is proposed. For a demerit control chart, an exact control limit can be obtained in special cases, but not in general. A proposed demerit control chart uses an Edgeworth Expansion to approximate the distribution of the demerit statistic and to compute the demerit control limits. A simulation study shows that the proposed method yields reasonably accurate results in determining the distribution of the demerit statistic and hence the control limits, even for small sample sizes. The simulation also shows that the performances of the demerit control chart constructed using the proposed method is very close to the advertised for all sample sizes. Since the demerit control chart statistic is a weighted sum of the nonconformities, naturally the performance of the demerit control chart will depend on the weights assigned to the nonconformities. The method of how to select weights that give the best performance for the demerit control chart has not yet been addressed in the literature. A methodology is proposed to select the weights for a one-sided demerit control chart with and upper control limit using an asymptotic technique. The asymptotic technique does not restrict the nature of the types and classification scheme for the nonconformities and provides an optimal and explicit solution for the weights. In the case presented so far, we assumed that the nonconformities are independent. When the nonconformities are correlated, a multivariate Poisson lognormal probability distribution is used to model the nonconformities. This distribution is able to model both positive and negative correlations among the nonconformities. A different type of multivariate control chart for correlated nonconformities is proposed. The proposed control chart can be applied to nonconformities that have any multivariate distributions whether they be discrete or continuous or something that has characteristics of both, e.g., non-Poisson correlated random variables. The proposed method evaluates the deviation of the observed sample means from pre-defined targets in terms of the density function value of the sample means. The distribution of the control chart test statistic is derived using an approximation technique called a multivariate Edgeworth expansion. For small sample sizes, results show that the proposed control chart is robust to inaccuracies in assumptions about the distribution of the correlated nonconformities. / Graduation date: 2004

M.Ing. / The Internet is evolving into a global communication infrastructure that is expected to support an overabundance of new applications such as IP telephony, interactive TV, and e-commerce. The existing best effort service is no longer sufficient. It is not enough to provide differentiated services and to meet QoS requirements of these different traffic types. As a result, there is an urgent need to provide more services that are powerful such as guaranteed services, flow protection etc, merged in one IP network, referred to as Integrated Services Packet-Switching Network (ISPN) in this thesis. To provide these services, QoS aware network architectures are required to implement the services. This dissertation presents a survey on two network architectures: Fair Queuing (FQ) and Scalable Core (SCORE), which attempt to provide QoS solutions in ISPN. We theoretically analyse scheduling as an important element in providing QoS in these architectures. The important thread in scheduling is performance and implementation complexity. SCORE based scheduling have less implementation complexity but cannot exactly match the high performance of FQ solutions, which suffer implementation complexity. The contribution of this work is a feedback protocol that minimises congestion in SCORE scheduling scheme called Core stateless fair queuing (CSFQ). The flow rates are adjusted by sending rate signal to a transmitting node from a receiving node, to adjust ill-behaved flow rate during congestion to a fair share rate of receiving node. We use CSFQ based theoretical analysis and simulations to demonstrate the performance of the feedback protocol.

M.Tech. (Operations Management) / It has become a trend for organisations to implement and certify quality systems. The most common quality system that organisations currently implement is ISO 9001. Certification to ISO 9001 has in recent times been used as a marketing tool to enter new markets. Nowadays, customers expect their suppliers and potential suppliers to be certified to ISO 9001. It has become a primary requirement for doing business, and customers now demand it. There have been various studies conducted to establish the advantages of ISO 9001 and its impact on organisational performance. Laboratories are no exception to this developing trend. They are implementing laboratory quality standards like ISO 17025 and the Organisation for Economic Cooperation and Development Good Laboratory Practice (OECD GLP). Some laboratories are now applying for certification of compliance to laboratory standards. Implementing and certifying laboratory systems is an exercise that comes at a cost. The exercise is demanding in terms of human resources, time and capital. There has not been a study conducted to evaluate the impact of these systems on the operational performance of laboratories. This is the reason that resulted in identification of the need to conduct the study. A qualitative research approach was pursued in conducting the study, where the researcher investigated the impact of laboratory quality standards on the operational performance of commercial and non-commercial laboratories. Operational performance in this study is defined as health and safety; supplier selection and performance; human resources; customer satisfaction and profitability. Data was collected through interviews, and was then summarised, and analysed in order to address the research problem. Based on the data collected, it was concluded there is no notable difference in the performance of laboratories with or without quality assurance systems such as ISO 17025 and OECD GLP.

The purpose of this study is to investigate specific contributing factors affecting quality assurance in the diagnosis of conventional cervical smears. More than half of South- African women fail to have one cervical smear in their lifetime and +/- 50 percent of those who do have cervical smears taken, are lost to follow-up. Since cervical cancer is the most common malignancy amongst women in developing countries, the medical profession will have to endeavor to screen a higher rate of women and ensure a 100 percent quality assurance with every patient treated in order to reduce the unacceptable high incidence of cervical carcinoma. At this stage it seems like an impossible task to screen all women in South Africa, due to far-off rural areas, shortage of medical professionals and the lack of knowledge of some women of the necessity of cervical smears. Many newly qualified South-African doctors leave the country to go and work elsewhere. South Africa then in turn has to recruit doctors from other countries to staff the State hospitals and clinics. Some areas have one doctor to thousands of patients, insufficient nursing personnel and inadequate equipment. Doctors in some areas cannot cope with the volume of work and the long hours. One has to accept that the quality of the management of some patients is affected negatively. There are a number of medico-legal issues (world wide) in relation to aspects of cervical cancer prevention practices which are controversial and are of particular concern to all of those involved in cervical cancer prevention. Various countries have therefore formed different national organizations to address the medico-legal issues in screening for the prevention of cancer. These organizations monitors procedures, internal quality control as well as external quality control. In South Africa, medico-legal cases are not so prevalent, but may become so shortly. The South-African medical professionals therefore have to ensure that their quality of work conforms to accepted good practice in all circumstances. State hospitals serve thousands of patients per month and it is an every day occurrence to see long queues of patients sitting waiting for doctors and who often have to come back the following day. The situation appears to be much improved in private practice and since patients have medical cover and accessible medical facilities. Since cervical cancer is the most common malignancy amongst women in developing countries, the medical profession will have to endeavor to screen a higher rate of women and ensure a 100 percent quality assurance with every patient treated in order to reduce the unacceptable high incidence of cervical carcinoma. At this stage it seems like an impossible task to screen 100 percent of women in South Africa, due to far-off rural areas, the shortage of medical professionals and ignorance of patients. Quality assurance is therefore of paramount importance to every medical professional for every patient treated. Laboratories all worldwide have been, or are in the process of being accredited by their specific accreditation authorities. The main reason for this is improvement of quality control and therefore quality assurance. The South African National Accreditation Society (SANAS) now accredits various laboratories in South Africa with the view of accreditting all laboratories within a certain time limit. The Ampath laboratory Port Elizabeth was successfully accredited during 2001. Accredited laboratories have to uphold a very high degree of quality to remain accredited. A team of professionals inspects the laboratory every 2 years and other quality assurance staff inspects the laboratories every few months. All aspects of the laboratory are checked, e.g. the qualification of staff, their registration with the Health Professions Council of South Africa (HPCSA), their curriculum vitaes, equipment, safety of the laboratory etc. Since the laboratory chosen for this study, is accredited, the author evaluated every cervical smear that was received in the laboratory since the year 2000, with the following objectives in mind: · Whether the presence or absence of an endocervical component has an effect on the adequacy of cervical smears · To determine the effect of using smaller coverslips on quality assurance in the cytology laboratory · Evaluate the effect that manual re-screening of smears has on quality assurance in the cytology laboratory. As there is a shortage of cytotechnologists and pathologists worldwide, several countries make use of automated screening devices as primary screening or secondary screening for quality assurance. These devices were tested in some laboratories in South Africa but were found to be very expensive and sensitivity and specificity were not up to standard. Sensitivity is a measure of the ability of a test to detect the abnormal - Sensitivity is the ratio of true positives to true positives + false negatives. Specificity is a measure of the ability of a test to correctly identify the negative - Specificity is the ratio of true negative to true negatives + false positives. The automated screening machines failed to identify abnormal cells amongst inflammatory cells, as well as in very blood stained smears. Several other problems also occurred and an increasing number of smears had to be manually rescreened, thus making this exercise costly and not helpful as a quality assurance instrument. The slides used for this thesis, have been retrieved from the archives of the Ampath laboratory in Port Elizabeth. Fourteen specific contributing factors affecting quality assurance in the diagnosis of cervical smears are also discussed and conclusions and recommendations given.