Screening answers a single question:, Which of my factors matter? and we’re willing to lump everything together just to answer it with as few attempts as possible.
The «Maximum Number of Levels» setting offers a choice of 2 or 3, and completely changes the range of plans available.
Two-level : Tables L4, L8, L12, L16, and L20, depending on the number of factors. Up to 19 factors in 20 trials.
3 levels : the DSD (Final Screening Design), from DSD3 to DSD12, as well as L9 and L18. The factor table then requires three levels: min, midpoint, and max.
💡 DSD is the modern screening plan, and it’s worth learning about: with three levels and testing costs similar to those of a two-level plan, it partially detects the curvature and does not confuse main effects with second-order interactions. In practical terms, it avoids the classic pitfall of two-level screening—concluding that «this factor has no effect» when its response reaches a maximum within the range and yields the same value at both endpoints.
⚠️ A screening plan is not a modeling plan. It identifies potential factors; it does not strictly quantify their effects and is not designed for optimization. The «How to Choose?» wizard explicitly excludes it from these objectives: «Suitable only for screening, not for modeling or optimization.».