Modify variables for mixture designs

Stat > DOE > Modify Design > Modify variables > Specify

This topic applies to mixture designs.

Modify the component names and the process variable names and the process variable low and high values. Usually, you modify process variables because you did not specify levels for the variables during design creation. The default levels are set so that the low level is −1 and the high level is 1. For a correct analysis when you analyze the experiment, you must use Modify Design instead of typing the levels directly in the worksheet. For individual runs that have settings that differ from the planned settings, type changes in the worksheet.

For example, an engineer creates a mixture design to study the effects of metal components on tensile strength. During the design creation in Minitab, the engineer did not specify the component names, the process variable names, or the process variable levels. Thus, the components are specified as A, B, C, the process variable is specified as X1, and the process variable levels are coded so that the low level is −1 and the high level is 1. Before collecting the data, the engineer wants to specify the component names, the process variable names, and the process variable levels so that the settings are more meaningful.

Note

If you specified process variable levels when you created the design, you can use Display Design to change between coded and uncoded process variable levels.

Component
Lists the components in the design. This column does not take input.
Name
Enter text to change the name of the components.
Process Variables
Name
Lists the process variables in the design. This column does not take input.
Type
Shows whether the process variable is text or numeric. This column does not take input.
Low
Enter a value that describes the low value of the process variable. For instance, enter 50 for a numeric low value, or enter Low for a text low value.
High
Enter a value that describes the high value of the process variable. For instance, enter 100 for a numeric high value, or enter High for a text high value.
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