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8. Assessing Product Reliability
8.4. Reliability Data Analysis


How do you fit an acceleration model?

Acceleration models can be fit by either graphical procedures or maximum likelihood methods As with estimating life distribution model parameters, there are two general approaches for estimating acceleration model parameters:  The same comments and recommendations concerning these methods still apply. Note that it is even harder, however, to find useful software programs that will do maximum likelihood estimation across stress cells and fit and test acceleration models. 
Sometimes it is possible to fit a model using degradation data Another promising method of fitting acceleration models is sometimes possible when studying failure mechanisms characterized by a stress-induced gradual degradation process that causes the eventual failure. This approach fits models based on degradation data and has the advantage of not actually needing failures. This overcomes censoring limitations by providing measurement data at consecutive time intervals for every unit in every stress cell.
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