RMQSI Answers ForumCategory: Data Analysis and TestingComponent reliability with censored data
ralphkrips asked 15 years ago


I’m an engineering student and currently working on a project dealing with the availability of a complex technical system. I have access to about 50 datasets for the components of the system. My problem is that the available data is not actual “failure” data but only “preventive replacement” data. I’m looking for a method to approximate component reliability with the available data. I’ve so far only found methods where there is at least one actual failure. I would greatly appreciate any feedback on this subject.

Thank you very much in advance.

5 Answers
smorris answered 15 years ago

Take a look at using Weibull analysis. The non-failed items are “suspensions”, which Weibull analysis handles. Ideally you should have some failures in the data set to use the Weibull approach. However, if there are very few, there is an approach called WeiBayes that assumes a Weibull slope (beta), thereby allowing a Weibull analysis to be applied (see http://www.bobabernethy.com/case_study_Wang_Weibayes.htm).

ralphkrips answered 15 years ago

Thank you very much for your help,
I now have Dr. Abernethy’s “New Weibull Handbook”. I understand I have to use the one parameter Weibull distribution (WeiBayes) when my data consists of supsensions only. I can estimate a shape parameter. I would just like to compare it to some generic values. The only values I could find were posted by Barringer and Associates, Inc. Do you know any other “public” sources?
Concerning the estimation of eta, I have to partially differentiate the likelihood function. The resulting function is described in Dr. Abernethy’s book. Do you know a source where the partial differentiation is described step by step?

smorris answered 15 years ago

I would recommend that you give Paul Barranger a call/email and request permission to use. I know of no other “publis” sources.

Regarding “partial differentiation”, I do not have a specific reference that I can recommend (that provides “step-by-step” instruction); however, there are many good math/calculus books that describe this. I would go to a university library and browse some to see what fits your needs.

smorris answered 15 years ago

Yes, this is correct. Otherwise, you have to assume a failure when none really exists in order to prevent a divide by zero error.

seniyajw answered 13 years ago

Extrapolation of the ESS test data or to end life expectancy is very difficult because the rate of acceleration is probably impossible to estimate from these proof of concept, and not controlled from the point of view accelertion .