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Design Wizard How-To¶

This walkthrough uses the wizard to reach a design by answering questions instead of choosing a design type, and shows what it recommends for a common screening problem.

Use it when you know what the experiment has to achieve but not which design achieves it. The wizard drives the same generators every design type uses, so the sheet it produces is the sheet that design type would have produced.

Steps¶

QXL DOE New > Design Wizard.
Answer the questions in order. For a screening problem, say you have 7 factors, that they are all quantitative, and that you want to find which ones matter rather than model curvature.
On the recommendation page the wizard names the design it suggests and the run count that goes with it. Accept it, or move back and change an answer to see the recommendation change.
Name the factors and the output on the last two pages, and press Finish.

What you get¶

The same design the matching design type would have built. For seven quantitative factors screened for size, that is a design in the 8 to 12 run range rather than the 128 runs a full factorial needs.

The sheet does not record that a wizard built it. It records the design, so every later step behaves exactly as it would for a design built directly.

What changes the recommendation¶

Answer	Effect
more factors	pushes toward a screening design and a fraction rather than a full factorial
curvature matters	pushes toward three levels, a central composite or a Box-Behnken
a factor is categorical	rules out the designs that require quantitative factors
runs are expensive	pushes toward the smallest design that still answers the question

There is no data block on this page, and here is why¶

Every other How-To in this help system gives you a table to paste into Excel. This one cannot, and the reason is the wizard itself: what it hands you depends on the answers you give it, so a walkthrough cannot print the design in advance without running the wizard for you.

Once it has recommended a design, that design type's own How-To has the matrix to check against. For a seven factor screening problem the two it is choosing between are Plackett-Burman at 12 runs and a fraction of a two-level factorial at 8, and both of those pages carry their full array as a Copy for Excel block.

Things to try next¶

Go back and say curvature matters. The recommendation moves off a two-level design and onto one with a middle setting.
Say one factor is categorical. Designs that cannot hold a named-level factor drop out of the recommendation.
Build the recommended design directly from its own design type and compare the sheets. They match, which is the point: the wizard is a route to a design, not a different design.