User Manual for Credible Reliability Prediction

The ASQ Reliability Division published Credible Reliability Prediction (CRP) monograph from 2003 to 2014. Thanks to Dan Burrows, www.asqrd.org, for getting ASQ to allow the copyright to revert to the author. You can now read CRP. It's in a *.pdf at the bottom of the page https://sites.google.com/site/fieldreliability/credible-reliability-prediction. 

If you haven’t read CRP, here is a simple example of how to make a credible reliability prediction. Predict a new-product’s failure rate function, a(t;new), as a comparable old-products’ failure rate function times MTBF(old)/MTBF(new), where the MTBFs are predictions. Then a credible reliability prediction is P[Life > t] = exp[–INTEGRAL[a(s;new)ds], where the integral is from 0 to t and a(s;new) is failure rate function of the new product. This reliability prediction uses all information available at the time a new product is designed. Generations of products have proportional failure rate functions, because most reliability factors don't change; e.g., processes, customers, and environments. CRP also tells how to estimate old products’ failure rate functions; even if there’s no life data, using ships and returns counts, population data required by generally accepted accounting principles.

The *.docx version of this User Manual (link at bottom of this page) contains active images of Excel spreadsheets described in CRP and some new ones. Double-click on the spreadsheet images in the *.docx version to use the spreadsheets and see formulas. Unfortunately, copying the spreadsheet images and pasting them into Excel pastes values, not formulas. Ask for the workbooks containing the active spreadsheets described in this User Manual, or send your data and describe it. I will plug it in and send you the active spreadsheets and the results.

In addition to help with CRP, this User Manual contains a correction [sorry], recent developments, and what to do with credible reliability predictions:

·         MTBF prediction with storage followed by operation and with variable operating hours per calendar hour,

·         Spares required for a finite mission with repair,

·         Reliability management of failure rates,

·         MTBF and reliability prediction for redundant systems,  without constant failure rates,  with warm standby, Cox’ proportional hazards model and General Method of Data Handling (GMDH),

·         Reliability demonstration testing without unwarranted assumptions, and

·         Reliability centered maintenance failure rate classification and risk-based inspection.

Reality trumps predictions, and credible reliability predictions include reality. 

Open or download CRPUSRM1.docx for the latest version, It's bound to change.  Click on the image link to it to read it in a new tab. Pease let me know of errors, confusion, questions, and requests for clarification, pstlarry077@gmail.com. Thanks.