Use to specify information about the process variables. Process variables are experimental factors that are not part of the mixture but may affect the response. For example, the adhesive properties of a paint may depend on the temperature at which it is applied.
You can include up to seven two-level process variables in the mixture design. The process variables may be included as full or fractional factorial designs. The mixture design will be generated at each combination of levels of the process variables.
- Process Variables
- None: Select if you do not want to include any process variables to your design
- Number: Select to include process variables, then choose the number of variables from the list. When you specify a number of process variables, that number of rows becomes active for editing in the table below.
- Type of design
- Select the type of design (full or fractional factorial) for the process variables. The available designs depends on the number of process variables.
- Fraction number
- If you select a fractional factorial design, you can select the fraction you want to use. By default, Minitab uses the principal fraction.
- Enter text to change the name of the process variables. By default, Minitab names the process variables as X1,... ,Xn, where n is the number of process variables.
- Choose to specify whether the process variables are numeric or text.
- Enter the value for the low setting of each process variable. By default, Minitab sets the low level of all process variables to -1. Process variable settings can be changed to any numeric or text value.
- Enter the value for the high setting of each process variable. By default, Minitab sets the high level of all process variables to +1. Process variable settings can be changed to any numeric or text value.