Example of the Alias Matrix
In this example, you evaluate the alias matrix of a design.
1. Select Help > Sample Data Folder and open Design Experiment/Coffee Data.jmp.
2. Select DOE > Design Diagnostics > Evaluate Design.
3. Select Grind, Temperature, Time, Charge, and Station and click X, Factor.
You can also add Strength as Y, Response. However, specifying the response has no effect on the properties of the design.
4. Click OK.
5. Click the gray disclosure icon to open the Alias Matrix section.
Figure 16.16 Alias Matrix for Coffee Data.jmp
The design assumes a main effects model. You can see this by running the Model script in the data table. Consequently, in the Evaluate Design window’s Model section, only the Intercept and five main effects appear. The Alias Terms section contains the two-way interactions.
The Alias Matrix shows the Model terms in the first column defining the rows. The two-way interactions in the Alias Terms are listed across the top, defining the columns. Consider the model effect Temperature for example. If the Grind*Time interaction is the only active two-way interaction, the estimate for the coefficient of Temperature is biased by 0.333 times the true value of the Grind*Time effect. If other interactions are active, then the value in the Alias Matrix indicates the additional amount of bias incurred by the Temperature coefficient estimate.