Degradation Data Analysis with a Linear Regression Model

This example validates the results for a degradation analysis with a linear regression model in Weibull++ degradation folios.

The data set is from Example 13.10 on page 338 in the book Statistical Methods for Reliability Data by Dr. Meeker and Dr. Escobar, John Wiley & Sons, 1998.

The test is for the current (i.e., amperage) of a laser device. Failure is defined as a 10% increases in amperage.

The book provides a linear regression model, $$y=b+at\,\!$$, but the parameters of the model are not provided. Only the predicted failure times are given. These are: 3702, 4194, 5847, 6172, 5301, 3592, 6051, 6538, 5110, 3306, 5326, 4995, 4721, 5689, and 6102. A Weibull distribution is used to fit the data; however, the model parameters are not provided. Only a probability plot is given.


 * The following picture shows the parameters of the linear regression model for each unit.




 * The predicted pseudo failure times are shown next.




 * The predicted failure times in Weibull++ are slightly different from the values given in the book. Since the book does not provide the model parameters, we couldn’t compare the Weibulll++ results with the results in the book.


 * The next picture shows the parameters of the fitted Weibull distribution.