Custom Relationship

If you want to use a custom transformation to model the relationship between the lifetime event and the accelerating factor, use the Custom option. This option is found in the list under Relationship in the launch window. Enter comma delimited values into the entry fields for the location (μ) and scale (σ) parameters. For the Devalt.jmp sample data, an example entry for μ could be “1, log(:Temp), log(:Temp)^2”, and an entry for σ could be “1, log(:Temp)”, where 1 indicates that an intercept is included in the model. Select the Use Exponential Link check box to ensure that the sigma parameter is positive.

Figure 4.19 Custom Relationship Specification in Fit Life by X Launch Window 

After selecting OK, location and scale transformations are created and included at the bottom of the Estimates report section.

Figure 4.20 Weibull Estimates and Formulas for Custom Relationship 

For an example of how to use a custom transformation, see Custom Relationship Example. Analysis proceeds similarly to the Example of the Fit Life by X Platform, where the Arrhenius Celsius Relationship was specified.