Reliability Issues for DOD Systems Report of a Workshop (2002) / Chapter Skim
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4. Further Discussion and Next Steps
4. Further Discussion and Next Steps
Pages 70-78
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From page 70... ...
The final section begins with a summary of some of the discussion at the workshop on appropriate ways to think about and quantify the uncertainties that accompany the statistical modeling of a complex system, and then presents highlights from the closing panel discussion and a summary of the general discussion that followed. COLLABORATION BE/l WEEN STATISTIC~S AND THE DEFENSE COMMUNITY The successful early collaboration between the statistics and defense communities was epitomized by the achievements of the Statistical Research Working Groups during World War II.
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PHYSICS-OF-FAILURE MODELS AND METHODS FOR SEPARATELY MODELING FAILURES FROM DIFFERENT SOURCES While no session was devoted specifically to either greater use of physics-of-failure models (i.e., models that directly represent the physical basis for failure) in modeling reliability for defense systems or methods for separately modeling failures due to distinct sources, these two related topics arose repeatedly during various workshop sessions.
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From page 72... ...
Second, Frank Camm mentioned that failures in the field are overrepresented by poorly produced components, referred to as "bad actors," possibly resulting from a poorly controlled manufacturing process. Third, Bill Meeker noted that some failures are unpredictable (possibly because of changes in the manufacturing process)
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From page 73... ...
The prediction errors are then analyzed, often through development of a model of those errors as a function of the inputs. A candidate starting point for a prediction error model is that the prediction errors are normally distributed with parameters that are dependent on x, that is, y=y*
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From page 74... ...
should be organized at regular intervals to help keep DoD abreast of recent advances in reliability methods. A third panelist, Marion Williams, recommended that great care be exercised in using developmental test results in combination with opera
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The chapters of the RAM Primer cover basic definitions, reliability measures, test planning, reliability models and estimation, hypothesis testing and confidence intervals for reliability performance, data analysis, and reliability growth estimation. Also included are tables and charts for assistance in applying the methods described.
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a state-ofthe-art reference book that well-educated and well-trained professionals could use to remind themselves of various methods. The form selected depends to some extent on whether the users are likely to be inexperienced junior analysts or experienced analysts.
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A key challenge here is that reliability under operational conditions differs from that under laboratory conditions, and appropriate linkage of the two is essential for the best estimation. Several participants argued for greater use of reliability growth models that are consistent with the maturation process of test, analyze, and fix.
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From page 78... ...
Reinstitution of more active collaboration between the statistical and defense acquisition communities, along with leading to better statistical methods, could also increase the number of academics interested in the most pressing problems faced by the defense acquisition community. In addition, such collaboration could increase the chances of attracting highly trained statisticians to careers in defense testing and acquisition.
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