Stat > DOE > Mixture > Analyze Mixture Design > choose Backward Elimination > Terms > Options
Specifies the criteria for model selection.
Selected Terms: Shows the terms that you chose in the Terms dialog box to include in the model.
Forced Terms: Enter the terms that you want keep in the model regardless of their p-values.
Alpha to remove: Set the value of a for removing a term from the model.
Number of alternative terms to show: Type a number to display the next best alternate terms up to the number requested. If a new term is entered into the model, displays the term which was the second best choice, the third best choice, and so on.