Suppose that you had chosen a traditional screening design instead of the definitive screening design in Definitive Screening Design. This example compares the two designs in terms of confounding.
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Select DOE > Classical > Screening Design.
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Select Load Factors From the red triangle next to Definitive Screening Design.
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Click Continue.
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Select Choose from a list of fractional factorial designs.
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Click Continue.
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Click Continue.
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Open the Display and Modify Design > Aliasing of Effects outline.
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The Aliasing of Effects outline for the 16-run fractional factorial design shows that every two-factor interaction is confounded with at least one other two-factor interaction. In this fractional factorial design, the Ethanol*Time interaction is confounded with Methanol*pH. To determine which interaction is active, you need to run additional trials. If the factors had been entered in a different order, the Ethanol*Time interaction might have been aliased with two other two-factor interactions.
In the section Definitive Screening Design, you constructed a 17-run definitive screening design. The Color Map on Correlations for this DSD (Figure 6.4) shows that no two-factor interactions are confounded with any other two-factor interactions. For the fractional factorial design, there are seven instances of confounded two-factor interactions. If you suspect that there are active two-factor effects, the DSD is the better choice.