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Author

Sven Knoth

Other affiliations: European University Viadrina
Bio: Sven Knoth is an academic researcher from Helmut Schmidt University. The author has contributed to research in topics: Control chart & EWMA chart. The author has an hindex of 14, co-authored 63 publications receiving 701 citations. Previous affiliations of Sven Knoth include European University Viadrina.


Papers
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Book ChapterDOI
01 Jan 2004
TL;DR: A state of the art survey in Statistical Process Control (SPC) for dependent data will be given, showing that falsely assuming independence mostly leads to improper SPC schemes.
Abstract: A state of the art survey in Statistical Process Control (SPC) for dependent data will be given. First papers about the influence on and the modification of standard SPC schemes are written some decades ago. After that, in the end of the 1980s and during the 1990s the consideration of dependence in the field of SPC became very popular. It turned out, that falsely assuming independence mostly leads to improper SPC schemes. Therefore, one has to be aware of dependence.

85 citations

Journal ArticleDOI
TL;DR: This work exploits the collocation method and the product Nyström method and sees that collocation leads to higher accuracy than currently established methods.
Abstract: Originally, the exponentially weighted moving average (EWMA) control chart was developed for detecting changes in the process mean. The average run length (ARL) became the most popular performance measure for schemes with this objective. When monitoring the mean of independent and normally distributed observations the ARL can be determined with high precision. Nowadays, EWMA control charts are also used for monitoring the variance. Charts based on the sample variance S2 are an appropriate choice. The usage of ARL evaluation techniques known from mean monitoring charts, however, is difficult. The most accurate method--solving a Fredholm integral equation with the Nystrom method--fails due to an improper kernel in the case of chi-squared distributions. Here, we exploit the collocation method and the product Nystrom method. These methods are compared to Markov chain based approaches. We see that collocation leads to higher accuracy than currently established methods.

57 citations

Journal ArticleDOI
TL;DR: Exponentially weighted moving average (EWMA) control charts designed for monitoring the variance or the mean and the variance of a normally distributed variable are either based on the log transfor...
Abstract: Exponentially weighted moving average (EWMA) control charts designed for monitoring the variance or the mean and the variance of a normally distributed variable are either based on the log transfor...

47 citations

Journal ArticleDOI
TL;DR: There is a greater probability that industry-sponsored economic studies in the field of oncology tend to be cost-minimisation analyses, to investigate less likely diagnostic screening methods, and to draw positive qualitative conclusions about costs, as compared to studies supported by nonprofit organisations.
Abstract: The purpose of this analysis of health economic studies in the field of oncology was to investigate among sponsored studies whether any relationship could be established between the type of sponsorship and (1) type of economic analysis, (2) health technology assessed, (3) sensitivity analysis performed, (4) publication status, and (5) qualitative conclusions about costs. The Health Economic Evaluations Database (HEED, version 1995–2000) was searched on the basis of oncological ICD-9 codes, sponsorship, and comparative studies. This search yielded a total of 150 eligible articles. Their evaluations were prepared independently by two investigators, on the basis of specific criteria. When evaluators disagreed, a third investigator provided a deciding evaluation. There was no statistically significant relationship between the type of sponsorship and sensitivity analysis performed (P=0.29) or publication status (P=0.08). However, we found a significant relationship between the types of sponsorship and of economic analysis (P=0.004), the health technology assessed (P<0.0001), and qualitative cost assessment (P=0.002). Studies with industrial sponsorship were 2.56 (99% lower confidence interval (CI)=1.28) times more likely to involve cost-minimisation analyses, were 0.04 (99% higher CI=0.39) times less likely to investigate diagnostic screening methods, and were 1.86 (99% lower CI=1.21) times more likely to reach positive qualitative conclusions about costs than studies supported by nonprofit organisations. In conclusion, our results suggest that there is a greater probability that industry-sponsored economic studies in the field of oncology tend to be cost-minimisation analyses, to investigate less likely diagnostic screening methods, and to draw positive qualitative conclusions about costs, as compared to studies supported by nonprofit organisations.

41 citations


Cited by
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Journal ArticleDOI
TL;DR: In this paper, applied probability and queuing in the field of applied probabilistic analysis is discussed. But the authors focus on the application of queueing in the context of road traffic.
Abstract: (1987). Applied Probability and Queues. Journal of the Operational Research Society: Vol. 38, No. 11, pp. 1095-1096.

1,121 citations

Journal ArticleDOI
TL;DR: Stuart Coles’s book on the modeling of extreme values provides an introductory text on the topic, a modeling-oriented text with an emphasis on different types of data and analytical approaches, meant for individuals with moderate statistical background.
Abstract: The modeling of extreme values is important to scientists in such Ž elds as hydrology, civil engineering, environmental science, oceanography and Ž nance. Stuart Coles’s book on the modeling of extreme values provides an introductory text on the topic. It is a modeling-oriented text with an emphasis on different types of data and analytical approaches. The book is laid out in nine chapters. Following introductory material and discussion of necessary theoretical background are chapters on approaches to extreme values that focus on the different types of data that might be used in an extreme value analysis. These include models for block maximums, threshold models, models for data from stationary and nonstationary processes, and approaches based on point processes. A chapter covers analysis of multivariate extremes, and the Ž nal chapter brie y covers such topics as Bayesian inference, Markov chains, and spatial extremes. Although this is not a data-driven text, it does contain numerous examples and analyses. These examples are used to illustrate the methodology; I would have preferred to see more motivation and interpretation of the results of the analyses. Datasets and S-PLUS programs for the analyses in the text are available at a website. These are easy to use for those slightly familiar with S-PLUS. The appendix describes the programs and illustrates how to access data and use the programs. It also gives links to sites that provide other software. The text does not include problem sets; these would have been useful, especially if the text is to be used in coursework. The text by Reiss and Thomas (2001) contains more thoroughly analyzed datasets, although it is twice the length and not as streamlined as the text under review. The book is meant for individuals with moderate statistical background. Those with coursework in maximum likelihood methods should have no difŽ culty reading and comprehending the text. Overall, this is a good text for someone getting started in extreme value methods.

402 citations

Journal ArticleDOI
13 Apr 2010-Trials
TL;DR: In this article, a narrative review is presented to gain an overview of reporting bias in the medical literature, focussing on publication bias and selective outcome reporting, and the authors explore whether these types of bias have been shown in areas beyond the well-known cases noted above.
Abstract: Reporting bias represents a major problem in the assessment of health care interventions. Several prominent cases have been described in the literature, for example, in the reporting of trials of antidepressants, Class I anti-arrhythmic drugs, and selective COX-2 inhibitors. The aim of this narrative review is to gain an overview of reporting bias in the medical literature, focussing on publication bias and selective outcome reporting. We explore whether these types of bias have been shown in areas beyond the well-known cases noted above, in order to gain an impression of how widespread the problem is. For this purpose, we screened relevant articles on reporting bias that had previously been obtained by the German Institute for Quality and Efficiency in Health Care in the context of its health technology assessment reports and other research work, together with the reference lists of these articles. We identified reporting bias in 40 indications comprising around 50 different pharmacological, surgical (e.g. vacuum-assisted closure therapy), diagnostic (e.g. ultrasound), and preventive (e.g. cancer vaccines) interventions. Regarding pharmacological interventions, cases of reporting bias were, for example, identified in the treatment of the following conditions: depression, bipolar disorder, schizophrenia, anxiety disorder, attention-deficit hyperactivity disorder, Alzheimer's disease, pain, migraine, cardiovascular disease, gastric ulcers, irritable bowel syndrome, urinary incontinence, atopic dermatitis, diabetes mellitus type 2, hypercholesterolaemia, thyroid disorders, menopausal symptoms, various types of cancer (e.g. ovarian cancer and melanoma), various types of infections (e.g. HIV, influenza and Hepatitis B), and acute trauma. Many cases involved the withholding of study data by manufacturers and regulatory agencies or the active attempt by manufacturers to suppress publication. The ascertained effects of reporting bias included the overestimation of efficacy and the underestimation of safety risks of interventions. In conclusion, reporting bias is a widespread phenomenon in the medical literature. Mandatory prospective registration of trials and public access to study data via results databases need to be introduced on a worldwide scale. This will allow for an independent review of research data, help fulfil ethical obligations towards patients, and ensure a basis for fully-informed decision making in the health care system.

385 citations

Journal ArticleDOI
TL;DR: An overview and perspective of recent research and applications of statistical process monitoring, including health-related monitoring, spatiotemporal surveillance, profile monitoring, use of autocorrelated data, the effect of estimation error, and high-dimensional monitoring, among others are provided.
Abstract: This paper provides an overview and perspective of recent research and applications of statistical process monitoring.

282 citations