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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: Raghavendra madgulkar (madgulkar@rediffmail.com, raghav@ip.eth.net )
Date posted: Wed Apr 24 4:51:26 US/Eastern 2002
Subject: Reliability prediction
Message:
Hello, I am looking for a method to predict reliability if I know the failure rate for last quarters. Suppose the failure rate for last eight quarters is 7,8,13,25,23,25,27,24 and the products I shipped during this months is 1975,1675,1678,1196,1851,1522,1668,1223. How can I predict the failure rrate for next four quarters.I am not using any software for this.. Can anybody help me on this,,,,,,,,,,,,,,


Reply:

Subject: Unit Return Rate
Reply Posted by: B.W.Dudley (bdudley@alionscience.com )
Organization: Reliability Analysis Center
Date Posted: Thu Apr 25 14:16:29 US/Eastern 2002
Message:
Given that the information posted is failure returns for the specific quarter, as would be done for a warranty period, I tried a trend line based on returns per 100 shipped per quarter. My trend line shows that the next four quarter may have the following return rate per hundred units shipped: Quarter number 9 -- 2.2 returns / 100 shipped Quarter number 10 -- 2.4 returns / 100 shipped Quarter number 11 -- 2.6 returns / 100 shipped Quarter number 12 -- 2.75 returns / 100 shipped Your data seems to indicate that you may have some quality control problems as the items were better in the beginning intervals, i.e. return rate of 0.4 or 0.5 units per 100 shipped.


Reply:

Subject: Actuarial failure rates and forecasts
Reply Posted by: Larry George (pstlarry@attbi.com )
Organization: Problem Solving Tools
Date Posted: Sat May 4 19:39:49 US/Eastern 2002
Message:
I am sending nonparametric estimates of quarterly age-specific (actuarial) failure rates and actuarial forecasts of the next 4 quarters of returns by separate email. The nonparametric estimates are described at http://www.fieldreliability.com/ProdSpec.htm, and the actuarial forecasts are described at http://www.fieldreliability.com/PrRelAct.htm. Actuarial forecasts are more accurate and precise than time series extrapolations. Ships and returns are sufficient to make nonparametric estimates of reliability and failure rate functions, even with some missing data. Did production of this product begin 8 quarters ago? If not, then please tell when production began and try to estimate missing production.


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