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Activity Number:
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316
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Type:
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Invited
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Date/Time:
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Wednesday, August 11, 2004 : 10:30 AM to 12:20 PM
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Sponsor:
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Section on Quality and Productivity
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| Abstract - #300093 |
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Title:
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Phase I Analysis of Nonlinear Product and Process Quality Profiles
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Author(s):
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James D. Williams*+
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Companies:
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Virginia Polytechnic Institute and State University
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Address:
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Dept. of Statistics, Blacksburg, VA, 24061-0439,
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Keywords:
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multivariate statistical process control ; nonlinear regression ; functional data ; T^2 control chart
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Abstract:
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In many quality control applications, use of a single (or several distinct) quality characteristic(s) is insufficient to characterize the quality of a produced item. In an increasing number of cases, a response curve (profile), is required. Such profiles can frequently be modeled using linear or nonlinear regression models. In recent research others have developed multivariate T^2 control charts and other methods for monitoring the coefficients in a simple linear regression model of a profile. However, little work has been done to address the monitoring of profiles that can be represented by a parametric nonlinear regression model. Here we extend the use of the T^2 control chart to monitor the coefficients resulting from a nonlinear regression model fit to profile data. We give four general approaches to the formulation of the T^2 statistics and determination of the associated upper control limits for Phase I applications. We also consider the use of nonparametric regression methods and the use of metrics to measure deviations from a baseline profile. These approaches are illustrated using the vertical board density profile data presented in Walker and Wright (2002).
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