The data we fit is that of Watson and Smith (1985) on the failure stresses of single carbon fiber given on Table 4.1, Page 81 of your textbook.
The following screens shots show the steps that one goes through in JMP to fit the model.
Use the calculator to define a new column, Length^2:
After going to the check pop-up menu to get likelihood ratio tests and confidence intervals we get:
As we can see it seems that we need the Length^2 term.
