Change search
ReferencesLink to record
Permanent link

Direct link
Process capability analysis with focus on indices for one-sided specification limits
2006 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

In this thesis some aspects of process capability analysis are considered. Process capability analysis deals with how to assess the capability of manufacturing processes. Based on the process capability analysis one can determine how the process performs relative to its product requirements or specifications. An important part within process capability analysis is the use of process capability indices. This thesis focuses on process capability indices in the situation when the specification limits are one- sided. The thesis consists of a summary and three papers, of which one is already published in an international journal. The summary gives a background to the research area, a short overview of the three papers, and some suggestions for future research. In Paper I, the frequency and use of process capability analysis together with statistical process control and design of experiments, within Swedish companies hiring alumni students are investigated. We also investigate what motivates organisations to implement or not implement these statistical methods, if there are differences in use that can be related to organisational types and what will be needed to increase the use. One conclusion drawn from the results is that the students employed in the Swedish industrial sector witness a modest use of these statistical methods and use in other sectors hiring the alumni is uncommon. In Paper II we present a graphical method useful when doing capability analysis having one-sided specification limits. This is an extension of the process capability plots previously developed for two-sided specification intervals. Under the assumption of normality we suggest estimated process capability plots to be used to assess process capability at a given significance level. The presented graphical approach is helpful to determine if it is the variability, the deviation from target, or both that need to be reduced to improve the capability. In Paper III the situation with non-negative process data having a skew distribution with a long tail towards large values are considered, when an upper specification limit only exists and the target value is 0. No proper indices exist for this specific situation, which is common in practice. We contribute to this area by proposing a new class of indices designed for skew, zero-bound distributions when an upper specification only exists and the target value is 0. This new class of indices is simple and possesses properties desirable for process capability indices. Two estimators of the proposed index are studied and the asymptotic distributions of these estimators are derived. Furthermore, we consider decision procedures, based on the estimated indices, suitable for deeming the process capability or not.

Place, publisher, year, edition, pages
Luleå: Luleå tekniska universitet, 2006. , 100 p.
Series
Licentiate thesis / Luleå University of Technology, ISSN 1402-1757 ; 2006:71
Research subject
Mathematical Statistics with special emphasis on Industrial Statistic
Identifiers
URN: urn:nbn:se:ltu:diva-18016Local ID: 66176f60-8145-11db-aabe-000ea68e967bOAI: oai:DiVA.org:ltu-18016DiVA: diva2:991022
Note
Godkänd; 2006; 20061201 (haneit)Available from: 2016-09-29 Created: 2016-09-29Bibliographically approved

Open Access in DiVA

fulltext(730 kB)1 downloads
File information
File name FULLTEXT01.pdfFile size 730 kBChecksum SHA-512
e9e9a08cb57aa4a95b69b8fc7879cae0d68e7e0754c135cacc68ca22dcfda19c97a1255f68814667ea38b30a15667d9d9d80339d752b98b1c5eadaddde115708
Type fulltextMimetype application/pdf

Search in DiVA

By author/editor
Albing, Malin

Search outside of DiVA

GoogleGoogle Scholar
Total: 1 downloads
The number of downloads is the sum of all downloads of full texts. It may include eg previous versions that are now no longer available

Total: 9 hits
ReferencesLink to record
Permanent link

Direct link