Alias Terms

It is possible that effects not included in your assumed model are active. In the Alias Terms outline, add potentially active effects that are not in your assumed model but might bias the estimates of model terms. Once you generate your design, the Alias Matrix outline appears under Design Evaluation. The Alias Matrix entries represent the degree of bias imparted to model parameters by the effects that you specified in the Alias Terms outline. See the The Alias Matrix in the Technical Details section.

By default, the Alias Terms outline includes all two-way interaction effects that are not in your Model outline (with the exception of terms involving blocking factors). Add terms using the buttons. For a description of how to use these buttons to add effects to the Alias Terms table, see Model.

Note: For interaction terms, only interactions of the selected order are added. This differs from the Model outline where interactions of the selected order and all lower orders are added to the model.

For example, suppose that you specify a design with three continuous factors. Your assumed model, specified in the Model outline, contains only those three main effects. You can afford only six runs. You want to see how estimates of the main effects might be biased by active two-way interactions and the three-way interaction.

The Alias Terms table includes all two-way interactions by default. You can add the three-way interaction by selecting Interactions > 3rd.

Figure 4.22 Alias Terms Outline 

Once you specify six runs in the Design Generation outline and click Make Design, the Design Evaluation outline appears. Open the Design Evaluation outline and the Alias Matrix outline.

Figure 4.23 Alias Matrix 

The Alias Matrix indicates that each main effect is partially aliased with two of the interactions. See Alias Matrix in the Evaluate Designs section and The Alias Matrix in the Technical Details section.