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Forum: Reliability & Maintainability Questions and Answers

Topic: Reliability & Maintainability Questions and Answers

Topic Posted by: Reliability & Maintainability Forum (src_forum@alionscience.com )
Organization: System Reliability Center
Date Posted: Mon Aug 31 12:47:36 US/Eastern 1998

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Original Message:

Posted by: Beth
Organization:UPCO
Date posted: Tue Jul 22 20:38:09 US/Eastern 2003
Subject: Comparing Reliability
Message:
Reliability of old system is .9958, new system is .9938. How do I calculate the reduction? I don't seem to be getting the same answer a previous report indicates, so... the report indicated 37 % decrease and I do not know where that came from nor do I know if its correct.


Reply:

Subject: Reliability Comparisons
Reply Posted by: B.W.Dudley (bdudley@alionscience.com )
Organization: RAC
Date Posted: Wed Jul 23 14:39:10 US/Eastern 2003
Message:
I believe that the percent reduction is based on the mean-time-between-failure [MTBF] parameter rather then the reliability one. The two are related, for example if the time interval for the reliability is 100 hours, using your figures for reliability, the MTBF for each scenario is 23,760 hours and 16,079 hours. This works out to be about a 32% reduction.


Reply:

Subject: Comparing Reliability
Reply Posted by: Igor (sf_tigor@bezeint.net )
Date Posted: Wed Nov 19 14:35:33 US/Eastern 2003
Message:
You can evaluate the reliability degradation by comparing the UNRELIABILITY figures (U)that are calculated as 1 - RELIABILITY. The first U is 0.0042 and the second U is 0.0062. The UNRELIABILITY incresed by 47.6% (0.0062/0.0042). Consequently, the RELIABILITY decresed similarly.


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