Title page for ETD etd-04062010-133834

Type of Document Dissertation
Author Olteanu, Denisa Anca
Author's Email Address dolteanu@vt.edu
URN etd-04062010-133834
Title Cumulative Sum Control Charts for Censored Reliability Data
Degree PhD
Department Statistics
Advisory Committee
Advisor Name Title
Vining, G. Geoffrey Committee Co-Chair
Woodall, William H. Committee Co-Chair
Birch, Jeffrey B. Committee Member
Kowalski, Scott M. Committee Member
  • Censored Data
  • CUSUM Charts
  • Lifetime Data
  • Multinomial Distribution
  • Weibull Distribution
Date of Defense 2010-04-01
Availability unrestricted
Companies routinely perform life tests for their products. Typically, these tests involve running a set of products until the units fail. Most often, the data are censored according to different censoring schemes, depending on the particulars of the test. On occasion, tests are stopped at a predetermined time and the units that are yet to fail are suspended. In other instances, the data are collected through periodic inspection and only upper and lower bounds on the lifetimes are recorded. Reliability professionals use a number of non-normal distributions to model the resulting lifetime data with the Weibull distribution being the most frequently used. If one is interested in monitoring the quality and reliability characteristics of such processes, one needs to account for the challenges imposed by the nature of the data. We propose likelihood ratio based cumulative sum (CUSUM) control charts for censored lifetime data with non-normal distributions. We illustrate the development and implementation of the charts, and we evaluate their properties through simulation studies. We address the problem of interval censoring, and we construct a CUSUM chart for censored ordered categorical data, which we illustrate by a case study at Becton Dickinson (BD). We also address the problem of monitoring both of the parameters of the Weibull distribution for processes with right-censored data.
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