Comparing the Standard and Modified Gompertz Models

This example appears in the Reliability growth reference.

Using the data in the following table, determine whether the standard Gompertz or modified Gompertz would be better suited for analyzing the given data.

Solution The standard Gompertz Reliability vs. Time plot is shown next.



The standard Gompertz seems to do a fairly good job of modeling the data. However, it appears that it is having difficulty modeling the S-shape of the data. The modified Gompertz Reliability vs. Time plot is shown next. As expected, the modified Gompertz does a much better job of handling the S-shape presented by the data and provides a better fit for this data.