In the Evaluate Design report, the Alias Matrix addresses the issue of how terms that are not included in the model affect the estimation of the model terms, if they are indeed active. In the Alias Terms section, you list potentially active effects that are not in your assumed model but that might bias the estimates of model terms. The Alias Matrix entries represent the degree of bias imparted to model parameters by the Alias Terms effects. See Alias Terms.
The rows of the Alias Matrix are the terms corresponding to the model effects listed in the Model section. The columns are terms corresponding to effects listed in the Alias Terms section. The entry in a given row and column indicates the degree to which the alias term affects the parameter estimate corresponding to the model term.
In evaluating your design, you ideally want one of two situations to occur relative to any entry in the Alias Matrix. Either the entry is small or, if it is not small, the effect of the alias term is small so that the bias is small. If you suspect that the alias term might have a substantial effect, then that term should be included in the model or you should consider an alias optimal design.
For more information about the computation of the Alias Matrix, see “The Alias Matrix”. See also Lekivetz, R. (2014).
Note the following:
• If the design is orthogonal for the assumed model, then the correlations in the Alias Matrix correspond to the absolute correlations in the Color Map on Correlations.
• Depending on the complexity of the design, it is possible to have alias matrix entries greater than 1 or less than -1.