ISSN:0022-4065    

DOI:10.1080/00224065.1992.11979398

出版商:Taylor&Francis    

年代:1992

数据来源: Taylor

摘要:

This is the introductory article in a special issue of theJournal of Quality Technologydevoted to the topic of process capability analysis. Statistical issues generated by the current use of process capability indices are outlined. The contributions of the articles in this issue are highlighted, and the role of related statistical and graphical methods is discussed.

ISSN:0022-4065    

DOI:10.1080/00224065.1992.11979399

出版商:Taylor&Francis    

年代:1992

数据来源: Taylor

摘要:

Capability indices compare the actual performance of a manufacturing process to the desired performance. In practice these indices are estimated using sample data, often with quite small sample sizes. Thus, it is of interest to obtain confidence limits (in particular, lower bounds) for the actual capability index given a sample estimate. Several methods for computing lower confidence bounds for these indices are described. A geometric view of the problem is presented and used as a basis for evaluating the performance of the various methods.

ISSN:0022-4065    

DOI:10.1080/00224065.1992.11979400

出版商:Taylor&Francis    

年代:1992

数据来源: Taylor

摘要:

The indices Cp, Cpk, and Cpmare widely used to estimate whether a process is capable. Recently, techniques and tables were developed to construct lower 95% confidence limits for each index. These techniques, however, assume the underlying process is normally distributed, and processes that are modestly nonnormal do occur and can be hard to detect. Therefore, three nonparametric bootstrap lower confidence limits are proposed for each of these indices. A simulation using three distributions (one normal and two nonnormal) was conducted, and a comparison was made of the performances of the bootstrap and the parametric estimates. The simulation demonstrated that in the normal process environment the bootstrap confidence limits perform comparably to confidence limits based on normality and in nonnormal process environments the bootstrap estimates perform significantly better.

ISSN:0022-4065    

DOI:10.1080/00224065.1992.11979401

出版商:Taylor&Francis    

年代:1992

数据来源: Taylor

摘要:

The relationship between the capability index Cpmand the expected squared error loss provides an intuitive interpretation of Cpm. By putting the loss in relative terms a user needs only to specify the target and the distance from the target at which the product would have zero worth, or alternatively, the loss at the specification limits. Confidence limits for the expected relative loss are discussed, and a numerical illustration is given.

ISSN:0022-4065    

DOI:10.1080/00224065.1992.11979402

出版商:Taylor&Francis    

年代:1992

数据来源: Taylor

摘要:

In this paper we survey and critically comment on some basic concepts and notions relevant to the methodology dealing with process capability indices (PCI's). The emphasis is on distributional and inferential aspects. The intent is to contribute to the understanding and interpretation of these indices, if one is (unfortunately) required to use them. We regard them primarily as indicators of the expected proportion of nonconforming items, and not as having some relationship to arbitrary loss functions, as is currently the more fashionable viewpoint. New PCI's, related to the expected proportion of nonconforming items, are suggested.

ISSN:0022-4065    

DOI:10.1080/00224065.1992.11979403

出版商:Taylor&Francis    

年代:1992

数据来源: Taylor

ISSN:0022-4065    

DOI:10.1080/00224065.1992.11979404

出版商:Taylor&Francis    

年代:1992

数据来源: Taylor

摘要:

A computer program is presented for computing lower confidence limits for the process capability index Cpk. One of the methods implemented requires computation of the Q function introduced by D. B. Owen in 1965 to represent a bivariate noncentraltdistribution function. The Q function is also useful for computing the probability density function of the point estimator for Cpk, and a second program is presented for this purpose.

ISSN:0022-4065    

DOI:10.1080/00224065.1992.11979405

出版商:Taylor&Francis    

年代:1992

数据来源: Taylor

ISSN:0022-4065    

DOI:10.1080/00224065.1992.11979406

出版商:Taylor&Francis    

年代:1992

数据来源: Taylor

ISSN:0022-4065    

DOI:10.1080/00224065.1992.11979407

出版商:Taylor&Francis    

年代:1992

数据来源: Taylor