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Full-Text Articles in Engineering
Change-Point Methods For Overdispersed Count Data, Brian A. Wilken
Change-Point Methods For Overdispersed Count Data, Brian A. Wilken
Theses and Dissertations
A control chart is often used to detect a change in a process. Following a control chart signal, knowledge of the time and magnitude of the change would simplify the search for and identification of the assignable cause. In this research, emphasis is placed on count processes where overdispersion has occurred. Overdispersion is common in practice and occurs when the observed variance is larger than the theoretical variance of the assumed model. Although the Poisson model is often used to model count data, the two-parameter gamma-Poisson mixture parameterization of the negative binomial distribution is often a more adequate model for …
Statistical Process Control And Medical Surveillance. An Application With Liver Function Tests, Bryan D. Richardson
Statistical Process Control And Medical Surveillance. An Application With Liver Function Tests, Bryan D. Richardson
Theses and Dissertations
Traditionally, medical surveillance of liver disease generally involves a battery of tests. This research used multivariate analysis techniques to reduce the number of measures required to identify liver dysfunction and found using a Transferase Index (a combination of three tests; ALT, AST, and GGT) provided the most satisfying assessment, but the single best indicator, ALT, may be sufficient. Transferase Index and ALT criterion were both applied to SPC control charts. Through the use of statistical process control (SPC), this research identified work zones possessing signs of adverse effects to an individual's liver as a possible result of their work environment …
Statistical Process Control In Medical Surveillance. An Application Using Spirometry, Paul W. Mcaree
Statistical Process Control In Medical Surveillance. An Application Using Spirometry, Paul W. Mcaree
Theses and Dissertations
This research effort concentrated on applying statistical process control techniques to the results of seven years worth of spirometry exams of workers at Wright-Patterson AFB in helping the occupational health squadron identify potential work hazard areas. Each spirometry exam was classified as abnormal or normal based on a comparison with established normals or a significant loss of function from the previous year's exam for the individual. Each test was classified into the work area of the individual and the number of abnormalities per population of the work area was examined.
Methods For Monitoring Process Control And Capability In The Presence Of Autocorrelation, Daniel J. Zalewski
Methods For Monitoring Process Control And Capability In The Presence Of Autocorrelation, Daniel J. Zalewski
Theses and Dissertations
When standard control charts are applied to a process whose measurements of quality exhibit autocorrelation, the performance of those charts can be considerably different than that expected when no autocorrelation is present. To model this performance, the existing definitions of assignable and chance causes of variation are extended to account for the variation induced by the autocorrelation structure. The application of statistical thinking toward continuous process improvement using the proposed taxonomy is discussed. A method to select control limits which yield a specified average run length in the absence of assignable causes of variation and which is suitable for use …