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A brief introduction to basic multivariate economic statistical process control
Full text linkThesis (MComm)--Stellenbosch University, 2012.ENGLISH ABSTRACT: Statistical process control (SPC) plays a very important role in monitoring and improving
industrial processes to ensure that products produced or shipped to the customer meet the
required specifications. The main tool that is used in SPC is the statistical control chart. The
traditional way of statistical control chart design assumed that a process is described by a
single quality characteristic. However, according to Montgomery and Klatt (1972) industrial
processes and products can have more than one quality characteristic and their joint effect
describes product quality. Process monitoring in which several related variables are of
interest is referred to as multivariate statistical process control (MSPC). The most vital and
commonly used tool in MSPC is the statistical control chart as in the case of the SPC. The
design of a control chart requires the user to select three parameters which are: sample size,
n , sampling interval, h and control limits, k.Several authors have developed control charts
based on more than one quality characteristic, among them was Hotelling (1947) who
pioneered the use of the multivariate process control techniques through the development of a
2 T -control chart which is well known as Hotelling 2 T -control chart.
Since the introduction of the control chart technique, the most common and widely used
method of control chart design was the statistical design. However, according to Montgomery
(2005), the design of control has economic implications. There are costs that are incurred
during the design of a control chart and these are: costs of sampling and testing, costs
associated with investigating an out-of-control signal and possible correction of any
assignable cause found, costs associated with the production of nonconforming products, etc.
The paper is about giving an overview of the different methods or techniques that have been
employed to develop the different economic statistical models for MSPC.
The first multivariate economic model presented in this paper is the economic design of the
Hotelling‟s 2 T -control chart to maintain current control of a process developed by
Montgomery and Klatt (1972). This is followed by the work done by Kapur and Chao (1996)
in which the concept of creating a specification region for the multiple quality characteristics
together with the use of a multivariate quality loss function is implemented to minimize total
loss to both the producer and the customer. Another approach by Chou et al (2002) is also
presented in which a procedure is developed that simultaneously monitor the process mean
and covariance matrix through the use of a quality loss function. The procedure is based on the test statistic 2ln L and the cost model is based on Montgomery and Klatt (1972) as well
as Kapur and Chao‟s (1996) ideas. One example of the use of the variable sample size
technique on the economic and economic statistical design of the control chart will also be
presented. Specifically, an economic and economic statistical design of the 2 T -control chart
with two adaptive sample sizes (Farazet al, 2010) will be presented. Farazet al (2010)
developed a cost model of a variable sampling size 2 T -control chart for the economic and
economic statistical design using Lorenzen and Vance‟s (1986) model.
There are several other approaches to the multivariate economic statistical process control
(MESPC) problem, but in this project the focus is on the cases based on the phase II stadium
of the process where the mean vector, and the covariance matrix, have been fairly well
established and can be taken as known, but both are subject to assignable causes. This latter
aspect is often ignored by researchers. Nevertheless, the article by Farazet al (2010) is
included to give more insight into how more sophisticated approaches may fit in with
MESPC, even if the mean vector, only may be subject to assignable cause.
Keywords: control chart; statistical process control; multivariate statistical process control;
multivariate economic statistical process control; multivariate control chart; loss function.AFRIKAANSE OPSOMMING: Statistiese proses kontrole (SPK) speel 'n baie belangrike rol in die monitering en
verbetering van industriële prosesse om te verseker dat produkte wat vervaardig word, of na
kliënte versend word wel aan die vereiste voorwaardes voldoen. Die vernaamste tegniek wat
in SPK gebruik word, is die statistiese kontrolekaart. Die tradisionele wyse waarop statistiese
kontrolekaarte ontwerp is, aanvaar dat ‟n proses deur slegs 'n enkele kwaliteitsveranderlike
beskryf word. Montgomery and Klatt (1972) beweer egter dat industriële prosesse en
produkte meer as een kwaliteitseienskap kan hê en dat hulle gesamentlik die kwaliteit van 'n
produk kan beskryf. Proses monitering waarin verskeie verwante veranderlikes van belang
mag wees, staan as meerveranderlike statistiese proses kontrole (MSPK) bekend. Die mees
belangrike en algemene tegniek wat in MSPK gebruik word, is ewe eens die statistiese
kontrolekaart soos dit die geval is by SPK. Die ontwerp van 'n kontrolekaart vereis van die
gebruiker om drie parameters te kies wat soos volg is: steekproefgrootte, n , tussensteekproefinterval,
h en kontrolegrense, k . Verskeie skrywers het kontrolekaarte ontwikkel
wat op meer as een kwaliteitseienskap gebaseer is, waaronder Hotelling wat die gebruik van
meerveranderlike proses kontrole tegnieke ingelei het met die ontwikkeling van die
T2 -kontrolekaart wat algemeen bekend is as Hotelling se 2 T -kontrolekaart (Hotelling,
1947).
Sedert die ingebruikneming van die kontrolekaart tegniek is die statistiese ontwerp daarvan
die mees algemene benadering en is dit ook in daardie formaat gebruik. Nietemin, volgens
Montgomery and Klatt (1972) en Montgomery (2005), het die ontwerp van die kontrolekaart
ook ekonomiese implikasies. Daar is kostes betrokke by die ontwerp van die kontrolekaart
en daar is ook die kostes t.o.v. steekproefneming en toetsing, kostes geassosieer met die
ondersoek van 'n buite-kontrole-sein, en moontlike herstel indien enige moontlike korreksie
van so 'n buite-kontrole-sein gevind word, kostes geassosieer met die produksie van niekonforme
produkte, ens. In die eenveranderlike geval is die hantering van die ekonomiese
eienskappe al in diepte ondersoek. Hierdie werkstuk gee 'n oorsig oor sommige van die
verskillende metodes of tegnieke wat al daargestel is t.o.v. verskillende ekonomiese
statistiese modelle vir MSPK. In die besonder word aandag gegee aan die gevalle waar die
vektor van gemiddeldes sowel as die kovariansiematriks onderhewig is aan potensiële
verskuiwings, in teenstelling met 'n neiging om slegs na die vektor van gemiddeldes in
isolasie te kyk synde onderhewig aan moontlike verskuiwings te wees.Master
Integrating National Benchmark Test (NBT) diagnostics into data analytics reports
Full text linkStudent retention and academic success remain significant challenges in South African higher education (Council on Higher Education (CHE), 2023: 12), and the articulation gap between school and university has been identified as a central concern. Addressing these challenges requires data-driven evaluation techniques. These data-driven techniques, such as diagnostic assessments, use empirical information to make important decisions affecting students’ educational progress, help teachers improve their educational curricula, and identify areas requiring improvement by monitoring and integrating information relating to a student’s educational progress (Aburizaizah, 2021). The Diagnostic Mathematics Information for Student Retention and Success (DMISRS) project was initially conceptualised to explore the articulation gap between students’ Grade 12 exit level skills in the areas of mathematics, academic literacy and quantitative literacy and the entry-level demands of higher education study, and to investigate ways of addressing this gap. A key subproject of the DMISRS project examined the influence of National Benchmark Test (NBT) subdomains on student success and how this diagnostic information could be shared and used by educators across the sector. The NBT consists of three domains: Academic Literacy (AL), Quantitative Literacy (QL), and Mathematics (MAT), each with specific subdomains. Subdomain analyses and relative importance analyses (RIA) provide granular insights into student performance, highlighting the relevance of subdomains for course success and the skills students need to succeed. By identifying areas needing attention, these analyses provide educators with information that they can use to tailor student support and effectively adapt their classroom practices. These analyses are situated within an Integrated Framework of Diagnosis, which integrates assessment inputs, analytical methods, interpretation and reporting mechanisms, and application in teaching and learning. The framework emphasises the feedback loop among four components: diagnostics, feedback, remediation / interventions, and validation. This paper presents the integration of diagnostic information using case studies, which include RIA and subdomain performance analyses of a South African university’s data analytics system referred to as the Data Analytics for Student Success (DASS). It highlights how, with the appropriate support to link this diagnostic information with curricula, access to it can help inform teaching and learning support initiatives. Drawing on the DASS example and the DMISRS/NBT diagnostic project, the paper further demonstrates how such diagnostic outcomes can be mobilised to provide more targeted, curriculum-integrated forms of student support
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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