Example of Calculation of Alias Matrix Summary Values
This example illustrates the calculation of the values that appear in the Alias Matrix Summary section. In this example, you compare the two designs assuming that only main effects are active.
1. Select Help > Sample Index, click the Sample Index red triangle and select Open Sample > Script. Open Compare Same Run Size.jsl.
2. Right-click in the script window and select Run Script.
Two 13-run design tables are constructed:
– Definitive Screening Design
– Plackett-Burman
You are interested only in the Plackett-Burman design. This is the active table.
3. From the Plackett-Burman table, select DOE > Design Diagnostics > Evaluate Design.
4. Select X1 through X6 and click X, Factor.
5. Click OK.
6. Open the Alias Terms section to confirm that all two-factor interactions are in the Alias Terms list.
7. Open the Alias Matrix section.
Figure 17.37 Alias Matrix for Plackett-Burman Design
For each model term listed in the Effect column, the entry in that row for a given column indicates the degree to which the alias term affects the parameter estimate corresponding to the model term.
Figure 17.38 Alias Matrix Summary for Two Designs
To obtain the Alias Matrix Summary entry corresponding to X1, square the terms in the row for X1 in the Alias Matrix, average these, and take the square root. You obtain 0.2722.