Model Types

Main Effects

Main Effects + Interactions

Full Quadratic

Full Cubic

Full Quartic

STRATEGY for Windows does not support nonlinear models.

Select a model to use to interpolate predictions of product performance between the data points. Select a model which will be supported by your data.

For example, if you have a Plackett-Burnam screening design in DES file then you will select a Main Effects model because that design is capable only of showing a b0 and main effects. If you have data at the corners of a cube or some other interaction design then select the Main Effects + Interaction Model which contains main effects and two factor cross products.

Similarly select the quadratic model if your DES file contains data that will support the addition of Xi-squared terms. Sometimes your data will be planned to support some of these additional terms but not all. You will have the chance to suppress terms that your data will not support.

When in doubt, suppress your best idea of a model, then run STRATEGY for Windows’ regression computation. STRATEGY for Windows will proceed without hesitation if your data supports the model you selected. STRATEGY will stop and print diagnostics (in the regression output file) if your model cannot be computed from your data. If you do not understand those diagnostics, call Dave Doehlert.