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Forum: Reliability & Maintainability Questions and Answers

Topic: Reliability & Maintainability Questions and Answers

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

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Posted by:Jim Guzzio ( )
Organization:General Dynamics ATS
Date posted: Mon Sep 18 10:44:01 US/Eastern 2000
Subject: "Merged Failure Rate" Calculation
With respect to the "RAC Data Failure Rate Selection Screen," the User is only able to filter on the Part Type First, Second and Third-Level Modifiers, i.e., there is no provision for filtering on the absence or various combinations of these modifiers. Since the User does not have the ability to select just those rows in the table which he/she wishes to retain for determining the "Merged Failure Rate," it would be helpful to have the ability to perform this task externally. Unfortunately, the methodology required to do this does not appear to be contained in the documentation.

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Subject: "Merged Failure Rate" Calculation
Reply Posted by: David Dylis
Organization: Reliability Analysis Center (RAC)
Date Posted: Tue Sep 26 8:56:33 US/Eastern 2000
In my original response, I had forgotten to mention that we made a change to the methodology that centers around how data that does not have hours or failures is merged. The modification is as follows: 1. One failure is assumed for each record that does not have hours and failures associated with it. 2. The hours required to obtain the observed failure rate are calculated based on this 1 failure. (hours are in millions of hours) 3. The failure rates for these records continue to be used in the calculation of the geometric mean. 4. The calculated hours are now also used with other records that have hours and failurs when calculating the percentage of total hours associated with records having failures. If you have any questions, feel free to contact me.

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