In the Custom Design platform, you can create a continuous factor with more than two levels in one of two ways:
1. Leave the factor in the design as a continuous factor and add power terms for the factor to the model. Adding the quadratic term generates a value in the center of the high and low values (to make a three-level factor). Similarly, adding the 3rd power term generates two values between the high and low levels to make a four-level factor.
2. Add the factor into the design as a Discrete Numeric factor with three (or more) levels. With this method, you can specify exactly the value(s) that will be used for the other level(s) in the design. To be sure all values are used in the design, you need to change the Estimability from "If Possible" to "Necessary' for the appropriate power terms. For instance, if you use a three level discrete numeric factor, change the Estimability to "Necessary" for the quadratic term to make sure all three levels are generated.
Lastly, when the design data table is created, you can change the factor's Design Role column property to Continuous for analysis purposes, if desired. Click on the black asterisk next to the column name, then click on Design Role. This produces the Column Properties dialog where edits can be made.
[Previously JMP Note 35417]