Uniform Shell Design Type

The Uniform Shell Designs (USD) have very uniformly spaced points. The distance from the center to each other trial is the same for all trials; that is, all of the points lie on a sphere. This radius is also the distance from each point to its nearest neighbors.

USD’s were developed to be more well spread out and more economical than Central Composite designs. Since 1991, I-Optimal designs are available which are minimal (the ultimate in economy) or minimal plus extra for greater precision. I-Optimal designs are more economical than USDs.

The Uniform Shell Design Type is the same as the Box-Behnken for 3 factors, but is unique for other numbers of factors.