You can use the Model Specification section of the Degradation Data Analysis report to specify the model that you want to fit to the degradation data. There are two formats for the Model Specification controls.
Simple Linear Path
Used to model linear degradation paths, or nonlinear paths that can be transformed to linear. See Simple Linear Path.
Nonlinear Path
Used to model nonlinear degradation paths, especially those that cannot be transformed to linear. See Nonlinear Path.
To change between the two specifications, use the Degradation Path Style submenu from the Degradation Data Analysis red triangle menu.