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Activity Number: 481 - Modeling, Analysis, and Assessment
Type: Contributed
Date/Time: Wednesday, August 1, 2018 : 8:30 AM to 10:20 AM
Sponsor: Quality and Productivity Section
Abstract #330555 Presentation
Title: A Simulation Study of Process Capability Analysis on Processes with Multiple Normal Distributions
Author(s): Laura Lancaster*
Companies: SAS Institute Inc.
Keywords: Process Capability; Non-Normal; Normal Mixture Distributions
Abstract:

Process capability analysis assesses how well a process produces product that is within spec. The standard capability indices relate process performance to spec limits. A process must be in statistical control for these indices to have meaning, and to make inferences about conformance they require the assumption that the measurements come from a normal distribution. It is not uncommon for a process to go out of statistical control due to contamination by a sub-process. Ideally, this contamination could be detected and fixed. However, sometimes the contamination goes undetected or cannot be fixed. The resultant process will have non-normal data. This study will analyze our ability to determine process capability when a process is a mixture of normal distributions. We will compare the performance of two methods for calculating non-normal capability indices that require fitting a distribution as well as the performance of using the standard capability indices that assume normality. We will also study the performance of using a best fit algorithm to determine the distribution before assessing the capability. A variety of normal mixture distributions and sample sizes will be studied.


Authors who are presenting talks have a * after their name.

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