Design of Experiments Guide > Evaluate Designs > Evaluate Design Options
Publication date: 08/13/2020

# Evaluate Design Options

The Evaluate Design red triangle menu contains the following options:

Advanced Options > Split Plot Variance Ratio

Specify the ratio of the variance of the random whole plot and the subplot variance (if present) to the error variance. Before setting this value, you must define a hard-to-change factor for your split-plot design, or hard and very-hard-to-change factors for your split-split-plot design. Then you can enter one or two positive numbers for the variance ratios, depending on whether you have specified a split-plot or a split-split-plot design.

Advanced Options > Set Delta for Power

Specify a value for the difference you want to detect that is applied to Anticipated Coefficients in the Power Analysis report. The Anticipated Coefficient values are set to Delta/2 for continuous effects. For categorical effects, they are alternating values of Delta/2 and –Delta/2. For more information about power analysis, see Power Analysis.

By default, Delta is set to two. Consequently, the Anticipated Coefficient default values are 1 for continuous effects and alternating values of 1 and –1 for categorical effects. The default values that are entered as Anticipated Coefficients when Delta is 2 ensure these properties:

The power calculation for a numeric effect assumes a change of Delta in the response mean due to linear main effects as the factor changes from the lowest setting to the highest setting in the design region.

The power calculation for the parameter associated with a two-level categorical factor assumes a change of Delta in the response mean across the levels of the factor.

The power calculation for a categorical effect with more than two levels is based on the multiple degree of freedom F test for the null hypothesis that all levels have the same response mean. Power is calculated at the values of the response means that are determined by the Anticipated Coefficients. Various configurations of the Anticipated Coefficients can define a difference in levels as large as Delta. However, the power values for such configurations will differ based on the Anticipated Coefficients for the other levels.

Save Script to Script Window

Creates a script that reproduces the Evaluate Design window and places it in an open script window.