The Box Cox Y Transformation option fits transformations from λ = –2 to 2 in increments of 0.2. To choose a proper value of λ, the likelihood function for each of these transformations is computed. They are computed under the assumption that the errors are independent and normal with mean zero and variance σ2. The value of λ that maximizes the likelihood is selected. This value also minimizes the SSE over the selected values of λ.
1.
Select Help > Sample Data Library and open Reactor.jmp.
2.
Select Analyze > Fit Model.
3.
Select Y and click Y.
4.
Make sure that the Degree box has a 2 in it.
5.
Select F, Ct, A, T, and Cn and click Macros > Factorial to Degree.
6.
Click Run.
Box Cox Y Transformation
The plot shows that the best values of λ are approximately between 1.0 and 1.2. The value that JMP selects, using its 0.2 unit grid of λ values, is 1.124.

Help created on 9/19/2017